Submission #1152142

#	Time	Username	Problem	Language	Result	Execution time	Memory
1152142		KluydQ	Cat (info1cup19_cat)	C++20	51.25 / 100	287 ms	25900 KiB

cat

#include <bits/stdc++.h>
//#include "grader.h"
 
#define respagold ios_base::sync_with_stdio(0), cin.tie(0);
#define int long long
#define ll long long
#define int2 __int128_t
#define FOR( i, x, n, d ) for( int i = x; i <= n; i += d )
#define FORR( i, x, n, d ) for( int i = x; i >= n; i -= d )
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x.size())
#define pb push_back
#define ins insert
#define lb lower_bound
#define ub upper_bound
#define pii pair <int, int>
#define mkp make_pair
 
using namespace std;
 
const int N1 = 2e5 + 123;
 
int a[N1], b[N1], c[N1], n, m, k, z, w, ans, x, y, pos[N1];
vector <pii> v;

mt19937 rng( chrono::steady_clock::now().time_since_epoch().count());
 
int rand( int l, int r )
{
    uniform_int_distribution <int> uid( l, r );
    return uid( rng );
}
void swp( int i, int j )
{
	swap( a[i], a[j] );
	pos[a[i]] = i, pos[a[j]] = j;
}
void solve()
{
	cin >> n;
	v.clear();
	k = 0;
	
	FOR( i, 1, n, 1 ) cin >> a[i], b[i] = 0;
	
	FOR( i, 1, n, 1 )
	{
		if( a[i] != n - a[n - i + 1] + 1 )
		{
			cout << "-1\n";
			return;
		}
	}
	FOR( i, 1, n, 1 )
	{
		pos[a[i]] = i;
		if( i <= (n >> 1) && a[i] > a[n - i + 1] ) k ++, b[i] = b[n - i + 1] = 1;
	}
	if( k % 2 )
	{
		cout << "-1\n";
		return;
	}
	FOR( i, 1, n >> 1, 1 )
	{
		int ps = pos[i];
		if( ps == i || ps == n - i + 1 ) continue;
		
		int i1 = i, j1 = ps, i2 = n - i + 1, j2 = n - ps + 1;
		
		if( (j1 < j2 && a[j1] > a[j2]) || (j1 > j2 && a[j1] < a[j2]) ) swap(j1, j2);
		v.pb({ i1, j1 }), swp( i1, j1 ), swp( i2, j2 );
	}
	vector <pii> po;
	
	FOR( i, 1, n >> 1, 1 )
	{
		if( a[i] > a[n - i + 1] ) po.pb({ i, n - i + 1 });
	}
	FOR( i, 0, sz(po) - 1, 2 )
	{
		v.pb({ po[i].F, po[i + 1].S });
		v.pb({ po[i].F, po[i + 1].F });
	}
	cout << sz(v) << ' ' << sz(v) << '\n';
	for( auto i : v ) cout << min( i.F, i.S ) << ' ' << max( i.F, i.S ) << '\n';
}
signed main() 
{
//	freopen("connect.in", "r", stdin);
//	freopen("connect.out", "w", stdout);
	    
    respagold
    
    int test = 0;
    
    if( !test ) cin >> test;
	
	while( test -- )
	{
		solve();
	}
}
// solved by KluydQ  

• Subtask 1: 5.25 / 15
• Subtask 2: 10 / 10
• Subtask 3: 8.75 / 25
• Subtask 4: 15 / 15
• Subtask 5: 12.25 / 35