再发个next_permutation的

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin>>n;
    int arr[19];
    for(int i=1;i<=n;i++) arr[i]=i;
    do{
        for(int i=1;i<=n;i++){
            cout<<arr[i]<<" ";
        }
        cout<<endl;
    }while(next_permutation(arr+1,arr+1+n));
    return 0;
}