Submission #950322

#	Time	Username	Problem	Language	Result	Execution time	Memory
950322		pcc	Cat (info1cup19_cat)	C++17	0 / 100	256 ms	262144 KiB

cat

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>


const int mxn = 3e6+10;
int N;
int arr[mxn];
bitset<mxn> ch;
bitset<mxn> vis;
vector<pii> ans;
vector<pii> psyco;

void change(int a,int b){
	swap(arr[a],arr[b]);
	swap(arr[N-a+1],arr[N-b+1]);
	return;
}

void combine(int a,int b){
	ans.push_back(pii(a,b));
	change(a,b);
	return;
}

void work(int h){
	int now = min(arr[h],N+1-arr[h]);
	do{
		int nxt = min(arr[now],N+1-arr[now]);
		//cerr<<now<<":"<<nxt<<endl;
		if(ch[now]){
			ch[now] = ch[now]^1;
			ch[nxt] = ch[nxt]^1;
			ans.push_back(pii(now,N+1-nxt));
		}
		else{
			ans.push_back(pii(now,nxt));
		}
		now = nxt;
	}while(now != h);
	//for(int i = 1;i<=N;i++)cerr<<ch[i];cerr<<endl;
	return;
}

void calc(){
	vector<int> odds;
	for(int i = 1;i+i<=N;i++){
		if(vis[i])continue;
		psyco.push_back(pii(i,0));
		int now = i;
		do{
			vis[now] = true;
			psyco.back().sc += ch[now];
			int nxt = min(arr[now],N+1-arr[now]);
			now = nxt;
		}while(now != i);
		if(psyco.back().sc&1){
			odds.push_back(i);
			psyco.pop_back();
		}
	}
	for(int i = 1;i<odds.size();i++){
		combine(odds[0],odds[i]);
	}
	for(auto &i:psyco)work(i.fs);
	if(!odds.empty())work(odds[0]);
}

void solve(){
	for(int i = 0;i<=N;i++)vis[i] = ch[i] = false;
	ans.clear();
	cin>>N;
	for(int i = 1;i<=N;i++)cin>>arr[i];
	int f = 0;
	for(int i = 1;i+i<=N;i++){
		if(arr[i]+arr[N-i+1] != N+1){
			cout<<"-1\n";
			return;
		}
		if(arr[i]>arr[N-i+1]){
			f++;
			ch[i] = true;
		}
	}
	//for(int i = 1;i<=N;i++)cerr<<ch[i];cerr<<endl<<endl;
	if(f&1){
		cout<<"-1\n";
		return;
	}
	calc();
	cout<<ans.size()<<' '<<ans.size()<<'\n';
	for(auto &i:ans)cout<<i.fs<<' '<<i.sc<<'\n';
	return;
}

int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	int t;
	cin>>t;
	while(t--)solve();
}

Compilation message (stderr)

cat.cpp: In function 'void calc()':
cat.cpp:68:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |  for(int i = 1;i<odds.size();i++){
      |                ~^~~~~~~~~~~~

• Subtask 1: 0 / 15
• Subtask 2: 0 / 10
• Subtask 3: 0 / 25
• Subtask 4: 0 / 15
• Subtask 5: 0 / 35