开了O2优化能过,希望有大佬能解疑
by 23372k101 @ 2023-01-18 15:32:52
[@23372k101](https://www.luogu.com.cn/user/932640)
这道题我下载了一下#10的数据:
```cpp
20 0
```
却没有输出(输出为空)
所以可以加一个特判,修改后的代码为:
```cpp
#include<bits/stdc++.h>
using namespace std;
int n,r,a[22];
void dfs(int m,int startx){
for(int i=startx;i<=m+n-r;i++){
a[m]=i;
if(m!=r)dfs(m+1,i+1);
else{
for(int j=1;j<=r;j++)cout<<setw(3)<<a[j];
cout<<endl;
}
}
}
int main (){
cin>>n>>r;
if(r==0)return 0;//主要是这个问题
dfs(1,1);
return 0;
}
```
我试了一下这样,发现这样就可以不开O2过了
by sijiajun @ 2023-01-23 16:21:22
@[23372k101](https://www.luogu.com.cn/user/932640)
by sijiajun @ 2023-01-26 12:49:03
# [个人博客主页](https://www.ricemoon.cn/)
```cpp
#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
typedef pair<int, int> PII;
int n, r;
int path[30];
bool st[30];
void dfs(int u, int num)
{
if (u == r + 1)
{
for (int i = 1; i <= r; i ++) cout << setw(3) << path[i];
cout << endl;
}
for (int i = 1; i <= n; i ++)
{
if (!st[i] and i > num)
{
st[i] = true;
path[u] = i;
dfs(u + 1, path[u]);
st[i] = false;
path[u] = 0;
}
}
}
int main()
{
cin >> n >> r;
dfs(1, 0);
return 0;
}
```
by Roger_Spencer @ 2023-03-05 20:53:16
@[sijiajun](/user/501614) 感谢
by 23372k101 @ 2023-03-26 18:47:35
@[23372k101](/user/932640) 没事
~~正好相隔两个月:)~~
by sijiajun @ 2023-03-26 19:28:04