LeetCode_Path Sum II

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5             / \            4   8           /   / \          11  13  4         /  \    / \        7    2  5   1

return

[   [5,4,11,2],   [5,8,4,5]]

这道题和他的兄弟题目一样，都是DFS，但是我很困惑的是我的代码MLE，于是看了http://www.cnblogs.com/remlostime/archive/2012/11/13/2767760.html上的代码，发现我们的代码惊人的相似，但是他的AC了，郁闷，谁要是知道为什么？求讲解。

我的代码：

class Solution {public:    vector<vector<int> > pathSum(TreeNode *root, int sum) {        vector <vector <int>> result;        vector <int> path;        int currentSum=0;        pathSum(root,sum,result,path,currentSum);        return result;    }    //Memory Limit Exceed     void pathSum(TreeNode *root,const int &sum,vector<vector<int>> &res,        vector <int> &path,int &currentSum){            if(root==NULL){                return;            }            path.push_back(root->val);            //还没达到叶节点            currentSum+=root->val;            if (root->left!=NULL||root->right!=NULL){                pathSum(root->left,sum,res,path,currentSum);                pathSum(root->left,sum,res,path,currentSum);            }            else{                if(currentSum==sum){                    res.push_back(path);                }            }            currentSum-=root->val;            path.pop_back();    }};

AC代码：

class Solution {private:    vector<vector<int> > ret;public:    void dfs(TreeNode *node, int sum, int curSum, vector<int> a)    {        if (node == NULL)            return;                if (node->left == NULL && node->right == NULL)        {            if (curSum + node->val == sum)            {                a.push_back(node->val);                ret.push_back(a);            }            return;        }                a.push_back(node->val);        dfs(node->left, sum, curSum + node->val, a);        dfs(node->right, sum, curSum + node->val, a);    }        vector<vector<int> > pathSum(TreeNode *root, int sum) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        ret.clear();        vector<int> a;         dfs(root, sum, 0, a);        return ret;    }};

My Submissions for Path Sum II

Submit TimeStatusRun TimeLanguage14 minutes agoAccepted108 mscpp18 minutes agoMemory Limit ExceededN/Acpp19 minutes agoCompile ErrorN/Acpp24 minutes agoMemory Limit ExceededN/Acpp

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