[LeetCode]112. Path Sum

112. Path Sum
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.

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// 因为不需要记录路径，所以就很简单了，递归到叶节点即可/** * Definition for a binary tree node. * 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 == NULL && root->right == NULL && root->val == sum)            return true;        return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);    }};