AfterAcademy Blog and Publication

Average of Levels in Binary Tree

Given a binary tree, write a program to return the average value of the nodes on each level in the form of an array. The range of the node's value is in the range of 32-bit signed integer.

Admin AfterAcademy 5 Nov 2020

Find The Height Of a Binary Tree

Given a binary tree, write a program to find the maximum depth of the binary tree. The maximum depth is the number of nodes along the longest path from the root node to the leaf node. A leaf is a node with no child nodes.

Admin AfterAcademy 3 Nov 2020

LRU Cache Implementation

Design and implement a data structure for Least Recently Used(LRU) cache. Your data structure must support two operations: get(key) and put(). The problem expects a constant time solution

Admin AfterAcademy 13 Oct 2020

Letter Combinations of a Phone Number

Given a string str, containing digits from 2 - 9 inclusive, write a program to return all the possible letter combinations that the number could represent. This is a popular coding interview question based on backtracking and recursive approach.

Admin AfterAcademy 12 Oct 2020

Reverse a Stack Using Recursion

Given a stack of integers st, write a program to reverse the stack using recursion. This problem will clear the concept of recursion.

Admin AfterAcademy 6 Oct 2020

Reverse First K Elements Of A Queue

Given an integer K and queue Q of integers. Write a program to reverse the order of the first K elements of the queue. The other elements will be in the same relative order.

Admin AfterAcademy 5 Oct 2020

Validate Stack Sequences

Given two sequences pushed and popped with distinct values, write a program to return true if and only if this could have been the result of a sequence of push and pop operations on an initially empty stack.

Admin AfterAcademy 5 Oct 2020

Interleaving Strings

Given three strings S1, S2 and S3, write a program which checks whether S3 is an interleaving of S1 and S2. The problem is a typical dynamic programming problem.

Admin AfterAcademy 18 Jul 2020

Surrounded regions

Given a 2-D matrix board where every element is either 'O' or 'X', write a program to replace 'O' with 'X' if surrounded by 'X'. It is a famous problem based on the concept of flood fill algorithms

Admin AfterAcademy 23 Sep 2020

Recursive Insertion Sort

Write a program for the recursive implementation of Insertion Sort. Insertion Sort is used to sort a given array. This problem will sharpen your recursion skills.

Admin AfterAcademy 23 Sep 2020

When to Convert a 2-D DP array to 1-D DP array And How?

In which situation 2 dimensional DP can be dropped to 1 dimension? Is there any principle or regular pattern? This is a very important question when it comes to optimization of DP arrays. Let's find out.

Admin AfterAcademy 16 Sep 2020

Find Nth Factorial

Write a program to find the factorial of a given number n. n is a non-negative integer. Factorial of a non-negative integer n is the multiplication of all integers smaller than or equal to n.

Admin AfterAcademy 14 Sep 2020

Sort List - Merge Sort

Sort a linked list using Merge Sort. This is a very famous interview problem that demonstrates the concept of recursion. This problem is quite similar to Merge Sort in Arrays.

Admin AfterAcademy 12 Sep 2020

Smallest Multiple With 0s and 1s

You are given an integer n, write a program to find the smallest multiple of n which consists of 0 and 1. The resultant number could be quite large so return it in the form of a string. This problem is a good example of graph-based problems.

Admin AfterAcademy 11 Sep 2020

Detect and Remove Loop In A Linked List

You are given the head of a linked list which probably contains a loop. If the list contains a loop, you need to find the last node of the list which points to one of its previous nodes to create a loop and make it point to NULL, thereby removing the loop.

Admin AfterAcademy 9 Sep 2020

Knight on chessboard

Given a square chessboard of A x B size, the position of Knight (C, D) and the position of a target (E, F) is given. Write a program to find out the minimum steps a Knight will take to reach the target position. This problem is a good example of BFS algorithm.

Admin AfterAcademy 7 Sep 2020

Largest Element In An Array

Given an array arr[] of size n , write a program to find the largest element in it. To find the largest element we can just traverse the array in one pass and find the largest element by maintaining a max variable.

Admin AfterAcademy 4 Sep 2020

Merge Two BST

Given two binary search trees with root nodes as tree1 and tree2 of size n and m, write a program to return an array of integers that contains all the elements of tree1 and tree2 in non-decreasing order. The expected time complexity is O(m+n).

Admin AfterAcademy 1 Sep 2020

Odd Even Linked List

Given a singly linked list, write a program to group all odd nodes together followed by the even nodes. You should try to do it in place and the program should run in O(n) time complexity.

Admin AfterAcademy 21 Aug 2020

Time and Space Complexity Analysis of Algorithm

In this blog, we will learn about the time and space complexity of an Algorithm. We will learn about worst case, average case, and best case of an algorithm. We will also see various asymptotic notations that are used to analyse an algorithm. So, let's learn the algorithm of an algorithm.

Admin AfterAcademy 18 Dec 2019

Wave Array

You are given an unsorted array of integers(arr) of length n, write a program to sort it in wave form. The array elements in the resultant array must be such that arr[0] >= arr[1] <= arr[2] >= arr[3] <= arr[4] ... and so on. If there are multiple sorted orders in wave-form, return the one which is lexicographically smallest.

Admin AfterAcademy 20 Aug 2020

Merge Two Sorted Arrays

You are given two sorted arrays arr1[ ] and arr2[ ] of sizes m and n respectively. Write a program to merge them in such a way that the resultant array is sorted too.

Admin AfterAcademy 17 Aug 2020

Reverse Bits

Given a non-negative integer num, write a program to return the number obtained after reversing the bits of num.

Admin AfterAcademy 15 Aug 2020

Middle Of The Linked List

Given a non-empty, singly linked list with head node head, write a program to return a middle node of linked list. If there are even nodes, then there would be two middle nodes, we need to print second middle element.

Admin AfterAcademy 10 Aug 2020

Missing Number

Given an array arr[] consists of 0, 1, 2, 3, 4,.....n. But one of the numbers is missing in it. Write a program to find the number that is missing from the array.

Admin AfterAcademy 10 Aug 2020

Quick Sort

Sorting is a process of arranging items systematically. There are several ways to sort a list of items. A very useful sorting algorithm in all of the sorting algorithms is quicksort. Given an array of integers arr[], write a program to sort the array in ascending order using Quick Sort.

Admin AfterAcademy 10 Aug 2020

Combinations

Given two integers n and k, Write a program to return all possible combinations of k numbers out of 1 2 3 ... n. Elements in a combination must be in a non-descending order. The combinations themselves must be sorted in ascending order, i.e., the combination with the smallest first element should be printed first.

Admin AfterAcademy 8 Aug 2020

Distribute Candy Problem

There are N children standing in a line with some rating value. You want to distribute a minimum number of candies to these children such that: Each child must have at least one candy. The children with higher ratings will have more candies than their neighbours. Write a program to calculate the minimum candies you must give.

Admin AfterAcademy 8 Aug 2020

Search in a 2-D Matrix

You are given a matrix arr of m x n size. Write a program to searches for a value k in arr. This arr has the following properties: - Integers in each row are sorted from left to right. - The first value of each row is greater than the last value of previous row. This is a basic optimization problem that will clear the concept of searching.

Admin AfterAcademy 18 Jul 2020

Binary Search

Given a sorted integer array arr[] of n elements and a target value k, write a program to search k in arr[]. The famous binary search algorithm is easy to implement and the best optimization technique for performing searching operations

Admin AfterAcademy 18 Jul 2020

Combination Sum

Given an array of integers arr[] and a target number k, write a program to find all unique combinations in arr[] such that the sum of all integers in the combination is equal to k. This famous backtracking problem has previously been asked in Adobe, Amazon, Facebook.

Admin AfterAcademy 18 Jul 2020

Generate Parentheses

Given n pairs of parentheses, write a program to generate all combinations of balanced parentheses. You have to return a string array containing all possible cases.

Admin AfterAcademy 18 Jul 2020

Max Product Subarray

You are given an array arr[] with n elements. Write a program to find the contiguous subarray which has the largest product. It's a typical optimization problem.

Admin AfterAcademy 18 Jul 2020

Maximal Square

You are given a 2D binary matrix arr[][] filled with 0's and 1's. The array contains a square of 1's. So, you need to find that square and return its area. The problem is a great example for practicing dynamic programming for technical interviews.

Admin AfterAcademy 18 Jul 2020

Minimum Number Of Jumps To Reach End

Given an array of non-negative integers arr[] of length n, where each element represents the max number of steps that can be made forward from that element. You are initially positioned at the first index of the array. Write a program to return the minimum number of jumps to reach the last index of the array.

Admin AfterAcademy 18 Jul 2020

Partition Equal Subset Sum

Given a non-empty array of positive integers arr[ ]. Write a program to find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.

Admin AfterAcademy 18 Jul 2020

Recover Binary Search Tree-Interview Problem

Given a Binary Search Tree such that two of the nodes of this tree have been swapped by mistake. You need to write a program that will recover this BST while also maintaining its original structure

Admin AfterAcademy 16 Jun 2020

Largest Rectangle in a Histogram-Interview Problem

You are given an array of integers arr where each element represents the height of a bar in a histogram. Histogram is a graphical display of data using bars of different heights. The bars are placed in the exact same sequence as given in the array. You need to find the area of the largest rectangle found in the given histogram.

Admin AfterAcademy 16 Jun 2020

Word Ladder Problem

This is a typical graph problem that needs a proper understanding of building a graph and traversing on it using a breadth-first search.

Admin AfterAcademy 16 Jun 2020

Max Points On The Straight Line

Given N point on a 2D plane as pair of (x, y) coordinates, Write a program to find the maximum number of point which lie on the same line. This is a famous mathemtical problem and clears the concepts of problem related with XY planes.

Admin AfterAcademy 16 Jun 2020

Convert A Min Heap to Max Heap

Given array representation of min Heap, write a program to convert it to max Heap. This problem will clear the concepts of the heap and priority queue which is a very important concept of data structures.

Admin AfterAcademy 11 Jun 2020

Valid Anagram

Write a program to check whether the two strings are an anagram of each other or not. Like, "s" is an anagram of "t" if the characters of "s" can be rearranged to form "t". This simple problem will let you understand the concepts of string manipulation.

Admin AfterAcademy 11 Jun 2020

Minimum Spanning Tree

In this blog, we will learn about Minimum Spanning Tree. We will also discuss two algorithms which is used to find a minimum spanning tree.

Admin AfterAcademy 8 Jun 2020

Reverse An Array

Reverse a given array in-place. This question uses the concept of swapping.

Admin AfterAcademy 8 Jun 2020

Merge two Binary Trees - Interview Problem

This is an interview problem asked in companies like Amazon, Microsoft. The problem is to merge two binary trees. The overlapping nodes are replaced by the sum of corresponding nodes. We are discussing two ways of solving this.

Admin AfterAcademy 6 Jun 2020

Minimum Absolute Difference in a BST-Interview Problem

This is an interview problem asked in Google technical interview. Given a BST(Binary Search Tree) with non-negative values, write a program to find the minimum absolute difference between values of any two nodes.

Admin AfterAcademy 6 Jun 2020

Find the Closest Palindrome

Given an integer k, write a program to find the closest integer (not including itself), which is a palindrome.

Admin AfterAcademy 6 Jun 2020

Sliding Window Maximum

You are given an integer array arr of size n. Assume a sliding window of size k starting from index 0. In each iteration, the sliding window moves to the right by one position till n-k. Write a program to return an array representing the maximum number in all sliding windows.

Admin AfterAcademy 2 Jun 2020

Applications of Hash Table

Hashing is a way to store data into some data structure (generally Hash Table is used) in such a way that the basic operations on that data i.e. the insertion, deletion, and searching can be performed in O(1) time. It is one of the important concepts that every programmer and developer should know. In this blog, we will know some of the applications on Hash Table.

Admin AfterAcademy 2 Jun 2020

Matrix Chain Multiplication

Given a chain <M1, M2...Mn> of n two-dimensional matrices, write a program to fully parenthesize the product M1×M2×⋯×Mn in a way that minimizes the number of multiplications. It's a famous dynamic programming problem.

Admin AfterAcademy 2 Jun 2020

Longest Arithmetic Progression

The problem requires knowledge of dynamic programming and Arithmetic progression. Given a set of integers in an array A[] of size n, write a program to find the length of the longest arithmetic subsequence in A.

Admin AfterAcademy 2 Jun 2020

Gas Station Problem

There are N gas stations along a circular route, where the amount of gas at station i is arr[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). At the beginning of the journey, the tank is empty at one of the gas stations. Return the minimum starting gas station's index if you can travel around the circuit once, otherwise return -1.

Admin AfterAcademy 2 Jun 2020

All Nodes Distance K in Binary Tree

Find all nodes at a distance k from a target node. This problem requires the knowledge of tree data structure. Recursion and tree traversals would be the base of the solution for this problem.

Admin AfterAcademy 2 Jun 2020

Binary Tree Zig Zag Level Order Traversal

Given a binary tree, return the zigzag level order traversal of its nodes' values. (i.e, from left to right, then right to left for the next level and alternate between). The problem is a typical Interview problem based on Tree Traversal

Admin AfterAcademy 4 May 2020

Optimal Substructure and Overlapping Subproblems

In this blog, we will understand the optimal substructure and overlapping subproblems property. We will also discuss how the problems having these two properties can be solved using Dynamic programming.

Admin AfterAcademy 1 May 2020

Types of Linked List and Operation on Linked List

In this blog, we will discuss the types of linked list and basic operations that can be performed on a linked list.

Admin AfterAcademy 10 Feb 2020

Rotate Matrix

Given a square matrix, turn it by 90 degrees in the clockwise direction.

Admin AfterAcademy 11 Feb 2020

What are the operations implemented in tree and what are its applications?

Tree Data Structure supports various operations such as insertion, deletion and searching of elements along with few others. This blogs discussed those operations along with explaining its applications.

Admin AfterAcademy 11 Feb 2020

Merge K Sorted Lists

Merge k sorted linked lists and return it as one sorted list.

Admin AfterAcademy 10 Feb 2020

Longest Increasing Subsequence - Interview Problem

You are given an array A with N elements. You need to find the longest increasing subsequence in the array.

Admin AfterAcademy 7 Apr 2020

Linked List and its Properties

In this blog, we will discuss about the linear data structure called Linked Lists. We will discuss its properties, advantages, and disadvantages. So, let's get started

Admin AfterAcademy 10 Feb 2020

Greatest Common Divisor-Interview Problem

This is a mathematical problem asked in interviews of Google like companies. For solving such problems you need to have some math skills and also some idea of algorithms like Euclid's GCD algorithm.

Admin AfterAcademy 10 Feb 2020

Graph Traversal: Depth First Search

In this blog, we will learn Depth First Search that is used for Graph Traversal i.e. the Depth First Search is used to traverse each and every node of a graph. So, let's learn together.

Admin AfterAcademy 10 Feb 2020

Graph Traversal: Breadth First Search

In this blog, we will learn Breadth First Search that is used for Graph Traversal i.e. the Breadth First Search is used to traverse each and every node of a graph. So, let's learn together.

Admin AfterAcademy 10 Feb 2020

Divide & Conquer vs Dynamic Programming

Divide and Conquer and Dynamic Programming are two most used problem-solving skills in Data Structures. In this blog, we will see the similarities and difference between Dynamic Programming and Divide-and-Conquer approaches.

Admin AfterAcademy 10 Feb 2020

Check if the Singly Linked List is a Palindrome-Interview Problem

Given a Linked List, your task is to find whether the given singly linked list is a palindrome or not. This is an interview problem asked in many companies like Amazon, Microsoft, Adobe, Flipkart and other big companies.

Admin AfterAcademy 10 Feb 2020

Binary Search Tree: Introduction, Operations and Applications

Binary Search Trees is one of the most important variation of binary tree and is extremely useful in practical applications. The blog discusses the operations and applications of this powerful data structure

Admin AfterAcademy 11 Feb 2020

Topological Sorting

In this blog, we will discuss Topological sort in a Directed Acyclic Graph. We will discuss what is the Topological Sort, how can we find Topological Ordering, Illustration using a Directed Acyclic Graph, its pseudo-code, and its applications.

Admin AfterAcademy 1 May 2020

Merge Overlapping Intervals

You will be given a set of intervals in the form of a 2-D array, write a program to merge all the overlapping intervals, and return the array. This problem will clear the concept of intervals and Graph

Admin AfterAcademy 1 May 2020

Path Sum In Binary Tree

Given a binary tree and a sum, write a program to determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.Its an easy problem based on Binary tree traversal and a famous interview question

Admin AfterAcademy 1 May 2020

Maximum Product Of Three Numbers

write a program to find three numbers whose product is maximum and output the maximum product. This is a basic mathematical problem and requires logical skill to solve.

Admin AfterAcademy 1 May 2020

Check If Two Arrays Are Equal Or Not

Given two given arrays of equal length, Check if given arrays are equal or not. This is a tricky interview problem as, at first, this looks like problem-related to combinatorics but could be solved quickly upon thinking.

Admin AfterAcademy 1 May 2020

Dijkstra’s Algorithm

In this blog, we will discuss Dijkstra's Algorithm. We will discuss what is the Dijkstra's Algorithm, how can we find the shortest path from source to other vertices using Dijkstra's Algorithm in Graph, Illustration using an example, its pseudo-code.

Admin AfterAcademy 1 May 2020

Min Stack Problem

This is an interview problem asked in companies like Amazon, Microsoft, Yahoo and Adobe. The problem is to design a stack that will support push(), pop(), top() and getMin() operation in constant time. We will be discussing two different ways to approach this problem.

Admin AfterAcademy 1 May 2020

Search For A Range In Sorted Array

Given a sorted array A[] with possibly duplicate elements, write a program to find indexes of first and last occurrences of an element k in the given array. This question will clear your concept of Binary Search

Admin AfterAcademy 1 May 2020

Inversion Count in an Array-Interview Problem

Given an array of integers A[ ], if i < j and A[i] > A[j] then the pair (i, j) is called the inversion of an array A[ ]. You need to write a program to find the total counts of inversion in an array A[ ]. The inversion count of an array suggests how close the array is from being sorted. This problem has been asked in Amazon and Google's interview.

Admin AfterAcademy 1 May 2020

How to become Developer Student Clubs Leads?

If you want to share your knowledge with others and want to learn back from them, then you must be in some community. Developer Student Clubs is one such community by Google Developers. Learn how to become a Developer Student Clubs lead at your campus.

Admin AfterAcademy 8 Apr 2020

Heap Building and Heap Sort

Heap is a very useful data structure that every programmer should know well. The heap data structure is used in Heap Sort, Priority Queues. The understanding of heaps helps us to know about memory management. In this blog, we will discuss the various about Heap Building and Heap Sort.

Admin AfterAcademy 7 Apr 2020

Merge Sort

Merge sort is a divide-and-conquer algorithm based on the idea of breaking down a list into several sub-lists until each sublist consists of a single element and merging those sublists in a manner that results into a sorted list.

Admin AfterAcademy 18 Feb 2020

Longest Common Prefix

Find the LCP. This is a very famous interview problem and demonstrates the use of various approaches and techniques to solve.

Admin AfterAcademy 7 Apr 2020

Steps Of Problem Solving During Technical Interview

In this blog, we will discuss about the steps of problem solving during the technical interview and how to cross the first hurdle for a programmer to get into the software industry and land their dream job.

Admin AfterAcademy 11 Feb 2020

How to prepare for the Coding Interview?

Coding interview preparation plan and the topics that you should cover before your interview. It will help you to get a basic plan structure that you should manage and keep your schedule accordingly.

Admin AfterAcademy 18 Mar 2020

Implement Queue Using Stack-Interview Problem

This is an interview problem asked in companies like Microsoft, Amazon, Adobe, Flipkart, etc. Here, we need to implement Queue data structure using another data structure Stack. This problem is meant for testing the data structure knowledge.

Admin AfterAcademy 16 Mar 2020

Triplet With Zero Sum

Given an array arr[ ] of n integers, are there elements x, y, z in arr such that x + y + z = 0? Find all unique triplets in the array which gives the sum of zero. The problem is asked in many interviews and required do be solved in O(n^2) with constant space.

Admin AfterAcademy 30 Mar 2020

First Unique Character In A String

Given a string S, write a program to find the first non-repeating character in it and return its index. The problem needs to be solved in O(n) and needs the knowledge of a hash map to solve.

Admin AfterAcademy 30 Mar 2020

Everything you need to know about GSoC

In this blog, we will get to know everything about GSoC i.e. how to apply, when to apply, what are the benefits of GSoC, etc.

Admin AfterAcademy 5 Mar 2020

What is Backtracking?

This blog discusses the concept of Exhaustive Search and Backtracking.

Admin AfterAcademy 11 Feb 2020

Find an Element In a Bitonic Array

Given a bitonic sequence of n distinct elements, write a program to search a given element k in the bitonic sequence. Bitonic Sequence is a sequence of numbers that is first strictly increasing then after a point strictly decreasing.

Admin AfterAcademy 23 Mar 2020

Remove Nth Node From End of List

You are given a linked list, write a program to remove the nth node from the end of the list and return the head. This problem has been previously asked in Google and Amazon and requires the understanding of the linked list to solve it.

Admin AfterAcademy 6 Apr 2020

Sort A Stack Using Another Stack

Given a stack, you have to sort it in ascending order. You can use another stack if you need auxiliary space. The problem is asked in Google, Microsoft and Amazon and requires knowledge of Stack and recursion to solve it.

Admin AfterAcademy 6 Apr 2020

Edit Distance

Write an algorithm to find the minimum number of operations required to convert string S1 into S2.

Admin AfterAcademy 6 Apr 2020

Median in a Row-wise Sorted Matrix-Interview Problem

The problem is to find the median in a row-wise sorted matrix. This is an interview problem asked in companies like Amazon. There is a further constraints on extra space. We have discussed two possible solutions.

Admin AfterAcademy 6 Apr 2020

Sudoku Solver

This problem is based on the famous sudoku puzzle. A sudoku board of 9x9 is given and you are expected to fill it correctly. The problem requires knowledge of Backtracking. This is a typical backtracking problem.

Admin AfterAcademy 30 Mar 2020

Dynamic Programming vs Greedy Algorithms

These are two very useful and commonly used algorithmic paradigms for optimization and we shall compare the two in this blog and see when to use which approach.

Admin AfterAcademy 29 Feb 2020

Find Diameter of Binary Tree

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

Admin AfterAcademy 3 Mar 2020

How to traverse in a tree?

It is important to know traversal techniques in a tree before solving tree problems. We have discussed the 3 primary traversals in a tree at length in this blog with both recursive and iterative implementations.

Admin AfterAcademy 9 Jan 2020

Check for Balanced Parentheses in an Expression

This is a famous interview problem asked in companies like Amazon, Microsoft. Here the basic idea is to think of the data structure which can easily solve this problem.

Admin AfterAcademy 29 Feb 2020

What are Greedy Algorithms?

This blog deals with the introduction of greedy algorithms for beginners and enthusiasts.

Admin AfterAcademy 18 Feb 2020

Idea of Dynamic Programming

Dynamic Programming is one of the most commonly used approach of problem-solving during coding interviews. We will discuss how can we approach to a problem using Dynamic Programming and also discuss the concept of Time-Memory Trade-Off.

Admin AfterAcademy 7 Jan 2020

Introduction to Data Structures

Data structures are widely used in every aspect of computer science. Data structures are the way of organizing and storing data in a computer so that it can be used efficiently. In this blog, we will look into data structures, its types, operations and applications.

Admin AfterAcademy 19 Jan 2020

Lowest Common Ancestor of a Binary Search Tree

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST. This is a very famous interview problem and previously asked in Microsoft and Amazon.

Admin AfterAcademy 3 Mar 2020

Lowest Common Ancestor of a Binary Tree

Given a binary tree, write a program to find the lowest common ancestor (LCA) of two given nodes in the tree. The question is asked previously in Amazon, Facebook, Adobe and requires an understanding of tree data structure.

Admin AfterAcademy 3 Mar 2020

Introduction to Heaps in Data Structures

Heap is a very useful data structure that every programmer should know well. The heap data structure is used in Heap Sort, Priority Queues. The understanding of heaps helps us to know about memory management. In this blog, we will discuss the structure, properties, and array implementation of heaps.

Admin AfterAcademy 18 Feb 2020

Median of the Two Sorted Array of Same Size

There are two sorted arrays nums1 and nums2 of size n. Find the median of the two sorted arrays.

Admin AfterAcademy 29 Feb 2020

Rain Water Trapping

Given n non-negative integers representing an elevation map where the width of each bar is 1. Write a program to compute how much water it is able to trap after raining.

Admin AfterAcademy 3 Mar 2020

Priority Queues

Priority Queues are similar to queues where we insert an element from the back and remove an element from the front, but with one difference that the logical order of elements in the priority queue depends on the priority of the elements. In this blog, we will discuss the priority queues, its properties, its various implementations, and its applications. We will also analyze and compare the various implementations of the Priority Queue.

Admin AfterAcademy 18 Feb 2020

Queue and its basic operations

Queue is a necessary addition in a programmer's toolkit. We will discuss the basic design structure of queue and what operations are performed on it. This blog also discusses the implementation of queue using arrays and linked lists

Admin AfterAcademy 27 Dec 2019

Operations on Heaps

Heap is a very useful data structure that every programmer should know well. The heap data structure is used in Heap Sort, Priority Queues. The understanding of heaps helps us to know about memory management. In this blog, we will discuss various operations that are done on heaps.

Admin AfterAcademy 4 Mar 2020

What is recursion in programming?

Using recursion, certain problems can be solved quite easily. Several algorithms design techniques and data structures are based on recursive thinking.

Admin AfterAcademy 12 Dec 2019

Remove Duplicates in a Sorted Array-Interview Problem

This is an interview problem asked in companies like Google, Microsoft, Amazon. The problem is to remove duplicates from a sorted array or list.

Admin AfterAcademy 7 Feb 2020

Remove Duplicates From a Sorted Linked List-Interview Problem

This is an interview problem asked by companies like Myntra, Visa, Oracle, Adobe, etc. The problem is to remove the duplicate nodes from the given Linked List so that only unique nodes(with unique data values) are present.

Admin AfterAcademy 18 Feb 2020

Find the Square Root of a given Integer-Interview Problem

Given an integer, your task is to find the square root of the integer. For an integer x to be the square root of the given integer N, x*x must be equal to N. This is an interview problem asked in companies like Amazon, Microsoft and Facebook.

Admin AfterAcademy 29 Feb 2020

Minimum Cost Path - Interview Problem

This is a famous interview problem based on dynamic Programming. This question has been asked in big companies like Amazon. Here we need to find the path between the given source and destination that gives the minimum cost.

Admin AfterAcademy 10 Feb 2020

Array vs Linked List

Array and Linked List are the two most used data structures. It's really important to understand and compare the advantages and disadvantages of both array and linked list. In this blog, we will compare these two linear data structures. So let's get started.

Admin AfterAcademy 7 Feb 2020

Calculate power function

Calculate the value of x^n.

Admin AfterAcademy 7 Feb 2020

Binary Search Tree vs Hash Table

In this blog, we will see the difference between a binary search tree and a hash table. We will see which data structure should be used when to solve our problems.

Admin AfterAcademy 6 Feb 2020

Introduction to Graph in Programming

In this blog, we will learn about the Graph data structure that is used to store data in the form of vertices and edges. We will also see some of the properties, types, representation of graph.

Admin AfterAcademy 6 Feb 2020

Introduction to Arrays

The idea of this blog is to discuss the famous data structure called Array. An Array is one of the important data structures that are asked in the interviews. So, we will learn about arrays and we will also discuss about the idea of the dynamic array and its amortized analysis. So let's get started.

Admin AfterAcademy 6 Feb 2020

Introduction To Sorting Algorithms - Selection and Insertion sort

Sorting is a famous problem solving approach during the interview. In this blog, we are going to discuss about the insertion and selection sort algorithm.

Admin AfterAcademy 27 Jan 2020

Reverse a Linked List

The problem is about reversing a Linked List. We are given the head node of the Linked List and we have to return the reversed Linked List's head. This is an interview problem asked in companies like Microsoft, Amazon and Adobe.

Admin AfterAcademy 22 Jan 2020

Getting started with Competitive Programming

In this blog, we will see how to get started with Competitive Programming. Competitive Programming is very important because in every interview you will be asked to write some code. So, let's learn together.

Admin AfterAcademy 22 Jan 2020

Swap List Nodes in Pairs-Interview Problem

This is an interview problem asked in companies like Amazon and Microsoft. Given a Linked List you have to swap nodes of the list in pairs.

Admin AfterAcademy 20 Jan 2020

Convert Roman Numerals to Integers

This is a problem of converting roman numerals into corresponding integer values. This problem is asked by Amazon, Microsoft, Facebook in their interviews.

Admin AfterAcademy 16 Jan 2020

Minimum in a Sorted and Rotated array

You have a sorted and rotated array where elements are sorted and rotated circularly. Write a program to find the minimum element in the array.

Admin AfterAcademy 16 Jan 2020

The Concept of Hashing in Programming

In this blog, we will learn about the concept of hashing in programming. We will learn about Direct Address Table, Hash Table, Hash Function, a collision in Hash table. So, let's get started.

Admin AfterAcademy 15 Jan 2020

What is the difference between iteration and recursion?

Iteration and Recursion are programming methodologies with similar objective and thus one might seem trivial compared to another, but that's not the case. We will be discussing the important differences between iteration and recursion and how both are useful.

Admin AfterAcademy 19 Dec 2019

Minimum Absolute Difference in an Array

Given an array of distinct integers A[ ], write a program to find all pairs of elements with the minimum absolute difference of any two elements.

Admin AfterAcademy 13 Jan 2020

Fractional Knapsack Problem

This is an interview problem asked by companies like Amazon. This problem is based on Greedy Algorithm and is one of the very basic problem for understanding Greedy Algorithms.

Admin AfterAcademy 13 Jan 2020

Spiral Order Traversal of a Matrix

Given a matrix or a 2-d array, you have to traverse the matrix in a spiral order. This is an interview question asked by companies like Microsoft and Amazon.

Admin AfterAcademy 19 Dec 2019

What is the two pointer technique?

Two pointer approach is an essential part of a programmer’s toolkit, especially in technical interviews.

Admin AfterAcademy 18 Dec 2019

Find minimum and maximum value in an array - Interview Problem

Given an array A[] of size n, you need to find the maximum and minimum element present in the array.Your algorithm should make minimum number of comparisons.

Admin AfterAcademy 6 Oct 2019

Container With Most Water

Find two lines, which together with x-axis forms a container, such that the container contains the most water.

Admin AfterAcademy 5 Jan 2020

Minimum Coin Change-Interview Problem

This is an interview problem based on the concept of dynamic programming. This question has been asked in various companies. We are dealing with solutions based on recursion, memorization and dynamic programming.

Admin AfterAcademy 2 Jan 2020

What is a tree data structure?

Tree is a widely-used powerful data structure that is a viable addition to a programmer’s toolkit. We shall be discussing the types and properties of trees in this blog.

Admin AfterAcademy 8 Jan 2020

Climbing Stairs - Interview Problem

There is a staircase of N steps and you can climb either 1 or 2 steps at a time. You need to count and return the total number of unique ways you can climb the staircase. The order of steps taken matters.

Admin AfterAcademy 20 Dec 2019

Print All Subsets of a given set

Given an array of distinct integers S, return all possible subsets. The set is not necessarily sorted and the total number of subsets of a given set of size n is equal to 2^n.

Admin AfterAcademy 31 Dec 2019

Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place. After flattening, the left of each node should point to NULL and right should contain the next node in level order so that it resembles a singly linked list.

Admin AfterAcademy 24 Dec 2019

Reverse a Linked List from position M to N

This is an interview problem asked in companies like Amazon, Facebook and Microsoft. The problem is to reverse a linked list from position m to n and print the reversed linked list.

Admin AfterAcademy 27 Dec 2019

Stack and its basic Operations

Stack is a very useful concept that a good programmer could use for their benefit. We will be discussing the basic design of stack and the operations that can be performed on it. We shall be also discussing the implementation of stack.

Admin AfterAcademy 26 Dec 2019

Sorted Array to Balanced BST

Given an array where elements are sorted in ascending order, convert it to a height balanced BST. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differs by more than one.

Admin AfterAcademy 24 Dec 2019

Comparison of Sorting Algorithms

In this blog, we will analyze and compare different sorting algorithms on the basis of different parameters like Time Complexity, Inplace/Outplace, Stability, etc.

Admin AfterAcademy 25 Dec 2019

Analysis of Recursion in Programming

In this blog, we will analyze the recursive algorithm using Recurrence Tree Method, Master theorem. We will also discuss the advantages and disadvantages of recursion.

Admin AfterAcademy 24 Dec 2019

What is iteration in programming?

The repeated execution of some groups of code statements in a program is called iteration. We will discuss the idea of iteration in detail in this blog.

Admin AfterAcademy 17 Dec 2019

Maximum path sum in a binary tree

Given a non-empty binary tree, find maximum path sum. For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along with the parent-child connections.

Admin AfterAcademy 19 Dec 2019

Divide and Conquer Approach in Programming

In this blog, we will go into the insights of the famous problem-solving approach Divide and Conquer. We will discuss problems like binary search, merge sort and also implementation issues that can come in this approach.

Admin AfterAcademy 16 Dec 2019

Kth Largest Element in a BST-Interview Problem

Given a Binary Search Tree, find the Kth Largest element in the given tree.

Admin AfterAcademy 11 Dec 2019

Invert a Binary Tree - Interview Problem

Given a binary tree, invert the binary tree and return it. An inverted form of a Binary Tree is another Binary Tree with left and right children of all non-leaf nodes interchanged. You may also call it the mirror of the input tree.

Admin AfterAcademy 10 Dec 2019

Minimum Depth of Binary Tree - Interview Problem

Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

Admin AfterAcademy 8 Dec 2019

Sort an array in wavy order - Interview Problem

Given an array say A having n elements, the task is to sort the array in wavy manner. In wavy manner the array is in the form where A[0] >= A[1] <= A[2] >= A[3] <= A[4] >= …..

Admin AfterAcademy 8 Dec 2019

Find Missing Positive - Interview Problem

Given an array, find the smallest missing positive integer.

Admin AfterAcademy 4 Dec 2019

Merge Two Sorted Lists - Interview Problem

Merge two sorted linked lists and return it as a new sorted list. The new list should be made by splicing together the nodes of the first two lists.

Admin AfterAcademy 4 Dec 2019

Sort a linked list using Insertion Sort - Interview Problem

Sort a linked list using insertion sort and return its head.

Admin AfterAcademy 4 Dec 2019

Check if two strings are anagrams of each other - Interview Problem

Given two strings S1 and S2 of size m and n respectively, you need to check whether the two strings are an anagram of each other or not. S1 is an anagram of S2 if the characters of S1 can be rearranged to form S2.

Admin AfterAcademy 8 Oct 2019

Longest Consecutive Sequence - Interview Problem

Given an unsorted array A[] consisting of n integers, you need to find the length of the longest consecutive sequence of integers in the array.

Admin AfterAcademy 4 Oct 2019

Check for pair in an array with a given sum - Interview Problem

Write a program that, Given an array of n integers and given a number K, determines whether or not there exist two elements whose sum is exactly K.

Shubham Gautam 27 Sep 2019

Add Two Numbers as Lists - Interview Problem

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contains a single digit. Add the two numbers and return it as a linked list.

Admin AfterAcademy 18 Nov 2019

Find the length of largest subarray with 0 sum

Given an array A[] of n integer elements, find the length of the longest subarray with sum equals to 0.

Admin AfterAcademy 14 Nov 2019

Set Matrix Zeros - Interview Problem

Given a matrix, A of size M x N of 0's and 1's. If an element is 0, set its entire row and column to 0

Admin AfterAcademy 14 Nov 2019

Maximum Subarray Sum

You are given an array A[] with n elements. You need to find the maximum sum of a subarray among all subarrays of that array. A subarray of array A[] of length n is a contiguous segment from A[i] through A[j] where 0<= i <= j <= n.

Admin AfterAcademy 16 Oct 2019

Check if a binary tree is BST or not - Interview Problem

Given the root of a binary tree, check whether it is a binary search tree or not.

Admin AfterAcademy 12 Nov 2019

Move all the zeroes to the end - Interview Problem

Given an array A[] of n elements filled with several integers, some of them being zeroes, you need to move all the zeroes to the end.

Admin AfterAcademy 12 Nov 2019

Sort Characters By Frequency - Interview Problem

You are given a string S and its length L and you need to sort its characters based on their frequency. The characters in the output will be distinct and ordered based on their frequency in S, higher frequency comes first.

Admin AfterAcademy 8 Nov 2019

Find the most frequent element in an array - Interview Problem

Given an array A[] of size n, find the most frequent element in the array, i.e. the element which occurs the most number of times.

Admin AfterAcademy 5 Nov 2019

Find the next greater element for every element in an array - Interview Problem

Given an array A[] of size n, you need to find the next greater element for each element in the array. Return an array that consists of the next greater element of A[i] at index i.

Admin AfterAcademy 5 Nov 2019

Find the majority element in an array - Interview Problem

You are given an array A[] consisting of n elements. You need to find and return the number which appears more than n/2 times.

Admin AfterAcademy 28 Oct 2019

Remove Duplicates from an unsorted arrray

You are given an unsorted array A[] consisting of N elements and you need to remove all the duplicate elements from the array. All the elements in the resultant array must be unique.

Admin AfterAcademy 21 Oct 2019

Find whether an array is a subset of another array - Interview Problem

Given two integer array A[] and B[] of size m and n(n <= m) respectively. We have to check whether B[] is a subset of A[] or not. An array B is a subset of another array A if each element of B is present in A. (There are no repeated elements in both the arrays)

Shubham Gautam 25 Sep 2019

Search an element in a sorted and infinite array

You are given a sorted and infinite array A and an element K. You need to search for the element K in the array. If found, return the index of the element, else return -1.

Admin AfterAcademy 17 Oct 2019

Find the intersection of two unsorted arrays - Interview Problem

Given two integer arrays A[] and B[] of size m and n, respectively. We need to find the intersection of these two arrays. The intersection of two arrays is a list of distinct numbers which are present in both the arrays. The numbers in the intersection can be in any order.

Admin AfterAcademy 1 Oct 2019

Find the kth smallest element in an array

Given an array A[] of n elements and a positive integer K, find the Kth smallest element in the array. It is given that all array elements are distinct.

Admin AfterAcademy 12 Oct 2019

Why do students fail in Algorithms and Data Structure Interviews for Top Companies?

All over the world, millions of students are looking forward to pursuing a career in the field of computer science. Though a lot of learning resources are available online, still, most of the students are struggling to become good at it and crack the interview.

Shubham Gautam 29 Apr 2019