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.

**Problem Note**

- A leaf is a node with no children.

**Example 1**

```
Input: Given the below binary tree and sum = 22
5
/ \
4 8
/ / \
11 13 4
/ \ \
7 2 1
Output: true
Explanation: There exist a root-to-leaf path 5->4->11->2 which sum is 22.
```