LeetCode 0077 - Combinations

[
  [2,4],
  [3,4],
  [2,3],
  [1,2],
  [1,3],
  [1,4],
]

class Solution {
public:
    vector<vector<int>> combine(int n, int k) {
        vector<vector<int>> res;
        vector<int> tmp(k, 0);
        int index = 0;
        while(index >= 0){
            tmp[index]++;
            if(tmp[index] > n)
                index--;
            else if(index == k - 1)
                res.push_back(tmp);
            else
                index++, tmp[index] = tmp[index - 1];
        }
        return res;
    }
};