07_PathSum.py

# Question link - https://leetcode.com/problems/path-sum/description/?envType=study-plan-v2&envId=top-interview-150

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
        # For this , problem we need to travere a Tree in Inorder DFS 
        # So implementing the helper function 
        def Dfs(node , curSum):
            # Base case 
            if not node:
                return False

            # If node , then calculate the sum 
            curSum += node.val

            # If a leaf node 
            if not node.left and not node.right:
                # Just return boolean True and false
                return curSum == targetSum

            # If not leaf , call for both subtrees
            return ( Dfs(node.left, curSum) or Dfs(node.right, curSum))

        return Dfs(root, 0)