112.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.

	Note: A leaf is a node with no children.

	Example:

	Given the below binary tree and sum = 22,

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


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

class Solution(object):
    def hasPathSum(self, root, sum):
        """
        :type root: TreeNode
        :type sum: int
        :rtype: bool
        """
        if not root:
        	return False

        if not root.left and not root.right and root.val == sum:
        	return True

        return self.hasPathSum(root.left, sum-root.val) or self.hasPathSum(root.right, sum-root.val)