PathSum.py

# 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.
#
# For example:
# 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.
#
# Python, Python3 all accepted.


class PathSum:
    def hasPathSum(self, root, sum):
        """
        :type root: TreeNode
        :type sum: int
        :rtype: bool
        """
        return root is not None and (root.left is None and root.right is None and sum == root.val or self.hasPathSum(root.left, sum - root.val) or self.hasPathSum(root.right, sum - root.val))


class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None