《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.

思路

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     struct TreeNode *left;
*     struct TreeNode *right;
* };
*/
bool hasPathSum(struct TreeNode* root, int sum) {
//有效性检查
if(root==NULL){
return false;
}
if(root->left==NULL&&root->right==NULL){//到达叶子节点，判断是否等于sum
if(root->val==sum){
return true;
}
else{
return false;
}
}
else{
return hasPathSum(root->left,sum-root->val)||hasPathSum(root->right,sum-root->val);
}
}