这是板子，它很可爱

#include<bits/stdc++.h>
using namespace std;
const int mod=1e9;
const int N=1e6+5;
int n,m=10;
int d[N],p[N];
vector<pair<int,int>>  a;
int main(){
    // freopen("in","w",stdout);
    n=10;
    mt19937 rnd(time(0));
    for(int i=1;i<=n;++i){
    	d[i]=1;
	} 
    for(int i=1;i<=n-2;++i){
    	++d[p[i]=rnd()%n+1];
	}
    int now,pre;
	for(int i=1;i<=n;++i){
		if(d[i]==1){
			pre=now=i;
			break;
		}
	}
    for(int i=1;i<=n-2;++i){
        int f=p[i];
        a.push_back({now,f});
        if(--d[f]==1&&f<pre){
        	now=f;
		}
        else{
			while(d[++pre]!=1);
			now=pre;
		}
    }
    a.push_back({now,n});
    for(int i=0;i<a.size();i++){
    	cout<<a[i].first<<" "<<a[i].second<<endl;
	}
    return 0;
}

#include<bits/stdc++.h>
#include<windows.h>  
using namespace std;  
int main(){  
    int t=10;
    clock_t startTime,endTime;
    while(t--){ 
        system("data.exe > data.txt");  
        system("test.exe < data.txt > test.txt");  
        startTime = clock();
        system("std.exe < data.txt > std.txt");  
        endTime = clock();
        if(system("fc std.txt test.txt")){
			cout<<"Wrong Answer"<<endl;
			break;
		}
		else{
			cout<<"Accepted"<<endl;
		}
		cout<<"The run time is: "<<(double)(endTime-startTime)/CLOCKS_PER_SEC<<"s"<< endl;
    }  
    if(t==0) cout<<"no error"<<endl;  
    else cout<<"error"<<endl;
    return 0;  
}