Combination

Combination

题目：

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.

For example :

If n = 4 and k = 2, a solution is:[[2,4],[3,4],[2,3],[1,2],[1,3],[1,4],]

代码如下：

    void getSub(int n, int k, int start, vector<int>& solution, vector<vector<int> >& result) {        if (solution.size() == k) {            result.push_back(solution);            return;        }        for (int i = start; i <= n; i++) {            solution.push_back(i);            getSub(n, k, i + 1, solution, result);            solution.pop_back();        }    }

解题思路：

采用递归算法，用 solution 保存所需要的单个组合， result 保存所有产生的组合。