LeetCode： Path Sum 2

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]
]

This is a very elegant Solution: 

class Solution {
public:
    vector<vector<int> > solSet;
    vector<int> sol;
    void solve(TreeNode* root, int sum){
        if ( (root->left==NULL) && (root->right==NULL) && (sum-root->val==0) ) { 
            sol.push_back(root->val); 
            solSet.push_back(sol);      
            return;    
        }
        sol.push_back(root->val);
        if (root->left !=NULL){
            solve(root->left, sum-root->val);
            sol.pop_back();        //记住需要pop_back
        }
        if (root->right!=NULL){
        solve(root->right, sum-root->val);    
        sol.pop_back();
        }
         
    }
     
 
    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        sol.clear();
        solSet.clear();
        if (root==NULL) {return solSet;}
        solve(root, sum);
        return solSet;
    }
};

This problem deserved  to be rehacking