LeetCode Path Sum

题目

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.

 

 

求是否存在一条从根到叶节点的路径，使得路径上的点的和为指定的数。

dfs即可。

 

代码

/** * 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)//空return false;if(root->left==NULL&&root->right==NULL&&sum-root->val==0)//到达叶节点，且符合要求return true;if(hasPathSum(root->left,sum-root->val)||hasPathSum(root->right,sum-root->val))//递归return true;return false;    }};