[leetcode]: 112. Path Sum

1.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.
一棵二叉树，判断是否有一条从根节点到叶子节点的路径和为指定值。
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.

2.分析

DFS

3.代码

bool hasPathSum(TreeNode* root, int sum) {    if (root == NULL)        return false;    if (root->left == NULL&&root->right == NULL&&root->val == sum)        return true;    return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);    }