Given the
root
node of a binary tree, write a program to find its
minimum depth.
Problem Note
- The minimum depth is the number of nodes along the shortest path from the nearest leaf node to the root.
- A leaf is a node with no children.
Example 1
Input: Given a binary tree [10,5,15,null,null,11,6]
10
/ \
5 15
/ \
11 6
Output: 2
Explanation: Shortest path to leaf is 10 -> 5
Example 2
Input: Given a binary tree [1,null,2]
1
\
2
Output: 2
Explanation: Shortest path to leaf is 1 -> 2