---
tags: data_structure_python
---

# Path Sum <img src="https://img.shields.io/badge/-easy-brightgreen">

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

**Note:** A leaf is a node with no children.

<ins>**Example:**</ins>

Given the below binary tree and sum = 22,

      5
     / \
    4   8
   /   / \
  11  13  4
 /  \      \
7    2      1

return true, as there exist a root-to-leaf path ```5->4->11->2``` which sum is 22.

## Solution

# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    def hasPathSum(self, root: TreeNode, sum: int) -> bool:
        # DFS.
        if root is None:
            return False
        elif root.left is None and root.right is None:
            return sum - root.val == 0
        return self.hasPathSum(root.left, sum - root.val) or   
               self.hasPathSum(root.right,  sum - root.val)