[leetcode]Path Sum @ Python

最新推荐文章于 2025-09-11 19:19:55 发布

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最新推荐文章于 2025-09-11 19:19:55 发布

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文章标签：数据结构与算法 python

本文介绍了如何使用递归算法解决二叉树中路径和等于给定数值的问题，通过实例详细解析了解题思路和实现代码。

原题地址：https://oj.leetcode.com/problems/path-sum/

题意：

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.

解题思路：使用递归解决。

代码：

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

class Solution:
    # @param root, a tree node
    # @param sum, an integer
    # @return a boolean
    def hasPathSum(self, root, sum):
        if root == None:
            return False
        if root.left == None and root.right == None:
            return root.val == sum
        return self.hasPathSum(root.left, sum - root.val) or self.hasPathSum(root.right, sum - root.val)