【全排列】77. Combinations

全排列问题：

                    

class Solution {
public:

    vector<vector<int>> ans;
    void find(vector<int>& nums, int k, int n,int m)
    {
        if (nums.size() == k)
        {
            ans.push_back(nums);
            return;
        }
        else
        {
            for (int i = m; i < n; i++)
            {	
                    nums.push_back(i + 1);

                    find(nums, k, n,i+1);
                    nums.erase(nums.begin()+nums.size() - 1);				
            }
        }
        return;
    }
    vector<vector<int>> combine(int n, int k) {
        vector<int> nums;
        find(nums, k, n, 0);
        return ans;
    }
};