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>> res;
vector<vector<int>> combine(int n, int k) {
vector<int> temp;
BFS(temp,n,1,k);
return res;
}
void BFS(vector<int> &temp,int n,int cur,int k) //cur(1~n)
{
if(temp.size()==k) //如果长度为k，则返回结果
{
res.push_back(temp);
return;
}
for(int i=cur;i<=n;i++) //遍历cur后到n的元素
{
vector<int> tmp=temp;
tmp.push_back(i);
BFS(tmp,n,i+1,k);
}
}
};原文：http://blog.csdn.net/u011391629/article/details/52125690