leetcode77.组合

 

---

 

其实就是全排列问题

class Solution {
public:
int nn,kk;
vector<vector<int>> res;
vector<int>t;
int num=0;

void dfs(){
    if(num==kk){
        res.push_back(t);
        return;
    }
    int i;
    for(i=t[num-1]+1;i<=nn;i++){
        t.push_back(i);
        num++;
        dfs();
        num--;
        t.pop_back();
    }
}
    vector<vector<int>> combine(int n, int k) {
        nn=n;
        kk=k;
        int i;
        for(i=1;i<=n;i++){
        t.push_back(i);
        num++;
        dfs();
        num--;
        t.pop_back();
        }
        return res;
    }
};