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]
]

代码：

    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        vector<vector<int> > result;
        result.clear();
        if(root == NULL)
            return result;
        if(root->val == sum && root->left == NULL && root->right == NULL){
            vector<int> tmp(1, sum);
            result.push_back(tmp);
            return result;
        }
        vector<vector<int> > lresult = pathSum(root->left, sum-root->val);
        vector<vector<int> > rresult = pathSum(root->right, sum-root->val);
        int n = lresult.size();
        for(int i = 0; i < n; i++){
            vector<int> tmp = lresult[i];
            tmp.insert(tmp.begin(), root->val);
            result.push_back(tmp);
        }
        n = rresult.size();
        for(int i = 0; i < n; i++){
            vector<int> tmp = rresult[i];
            tmp.insert(tmp.begin(), root->val);
            result.push_back(tmp);
        }
        return result;
    }