[勇者闯LeetCode] 112. Path Sum

[勇者闯LeetCode] 112. Path Sum

Description

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

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

Information

• Tags: Tree | Depth-first Search
• Difficulty: Easy

Solution

使用深度优先搜索，遇到叶节点时判断路径的和是否与目标值相等。

Python Code

# Definition for a binary tree node.# class TreeNode(object):#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution(object):    def hasPathSum(self, root, sum):        """        :type root: TreeNode        :type sum: int        :rtype: bool        """        if root is None:            return False        if root.left is None and root.right is None and root.val == sum:            return True        else:            return self.hasPathSum(root.left, sum-root.val) or\                   self.hasPathSum(root.right, sum-root.val)