LeetCode:Combinations

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],
]

class Solution {
public:
    vector<vector<int> > combine(int n, int k) {
        vector<vector<int>> res;
        if(n<1||k<1||n<k)
            return res;
        vector<int> temp;
        collect(n,k,0,temp,res);
        return res;
    }
        void collect(int n,int k,int i,vector<int> &temp,vector<vector<int>> &res)
        {
            if(temp.size()==k)
            {
                res.push_back(temp);
                return;
            }
            for(;i<n;i++)
            {
                temp.push_back(i+1);
                collect(n,k,i+1,temp,res);
                temp.pop_back();
            }
        }
};

LeetCode:Combinations

原文：http://blog.csdn.net/wolongdede/article/details/44656685