113. 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]
]

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void pathSum(TreeNode* root,int gap,vector<vector<int>>& result,vector<int> cur){
        if(!root) return;
        cur.push_back(root->val);
        if(!root->left&& !root->right) {
            if(root->val==gap) result.push_back(cur);
        }
        pathSum(root->left,gap-root->val,result,cur);
        pathSum(root->right,gap-root->val,result,cur);
        cur.pop_back();
    }
    vector<vector<int>> pathSum(TreeNode* root, int sum) {
        vector<vector<int>> result;
        std::vector<int> cur;
        if(!root) return result;
        pathSum(root,sum,result,cur);
        return result;
    }
};