LeetCode_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.

这道题是一道很典型的DFS题目，题目一拿过来以为找到一个从根节点出发的路径，满足路径和为给定值就可以，结果贡献了一次WA，代码如下：

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;
}
bool result=false;
hasPathSumDFS(root,sum,0,result);
return result;
}
void hasPathSumDFS(TreeNode *root, const int &sum,int currentSum,bool &hasFound) {
//证明遍历到叶子节点也没有找到Root to Leaf sum=sum的路径
if (root==NULL){
return;
}
//已经找到了满足条件的路径直接返回
if (hasFound){
return;
}
if (root->left!=NULL||root->right!=NULL)
{
hasPathSumDFS(root->left,sum,currentSum+root->val,hasFound);
hasPathSumDFS(root->right,sum,currentSum+root->val,hasFound);
}
else{
if (root->val+currentSum==sum){
hasFound=true;
}
}
}
};

My Submissions for Path Sum

Submit Time	Status	Run Time	Language
30 minutes ago	Accepted	72 ms	cpp
33 minutes ago	Wrong Answer	N/A	cpp

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