Path Sum II

description:

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]
]

solve:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<vector<int> > res;
        vector<int> fk;
        //string tmp;
        //ostringstream ret;
        run(root, res, fk, 0, sum);

        return res;
    }
    void run(TreeNode* root, vector<vector<int> >& res, vector<int> ret, int total, int sum) {
        if(root == NULL) {
            return;
        }
        total += root->val;
        ret.push_back(root->val);
        if(root->right == NULL && root->left == NULL) {
            if(sum == total) {
                if(ret.size() > 0) {
                    res.push_back(ret);
                }
            }
            return;
        }
        //ret << root->val << ",";
        run(root->right, res, ret, total, sum);
        run(root->left, res, ret, total, sum);
    }
};