LeetCode (12) Path Sum (二叉树路径和判断)

题目描述

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.

因此，本题要求判断二叉树某一条路径的和是否为给定的数值。本题的思路为深度优先搜索。

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool hasPathSum(TreeNode *root, int sum) {        if (root == NULL)        {            return false;        }        if (!root->left && !root->right && root->val == sum)            return true;        if (hasPathSum(root->left, sum-root->val))            return true;        else if (hasPathSum(root->right, sum-root->val))            return true;        else            return false;            }};