leetcode Path Sum 路径和

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.

如果根节点为空，则返回false，如果不为空，且无左右子树，则判断当前和是否与根节点数据相等，否则递归：

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     struct TreeNode *left;
*     struct TreeNode *right;
* };
*/
bool hasPathSum(struct TreeNode* root, int sum) {
if(root==NULL)return 0;
if(root->left==NULL&&root->right==NULL)return sum==root->val;
return hasPathSum(root->left,sum-root->val)||hasPathSum(root->right,sum-root->val);

}