Submission #687059

#	Time	Username	Problem	Language	Result	Execution time	Memory
687059		Alihan_8	Cat (info1cup19_cat)	C++17	100 / 100	569 ms	29604 KiB

cat

#include <bits/stdc++.h>
// include <ext/pb_ds/assoc_container.hpp>
// include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
using namespace std;
#define all(x) x.begin(), x.end()
#define pb push_back
// define ordered_set tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>
#define mpr make_pair
#define ln '\n'
void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
#define int long long
void solve(){
    int n; cin >> n;
    vector <int> p(n), pos(n);
    for ( auto &i: p ) cin >> i, i--;
    vector <pair<int,int>> res;
    auto inv = [&](int i){
        return n-1-i;
    };
    auto answer = [&](int i, int j){
        int _i = inv(i), _j = inv(j);
        swap(p[i], p[j]), swap(pos[p[i]], pos[p[j]]);
        swap(p[_i], p[_j]), swap(pos[p[_i]], pos[p[_j]]);
        res.pb({i, j});
    };
    auto print = [&](){
        cout << (int)res.size() << ' ' << (int)res.size() << ln;
        for ( auto [l, r]: res ) cout << ++l << ' ' << ++r << ln;
    };
    for ( int i = 0; i < n; i++ ) pos[p[i]] = i;
    vector <int> rem;
    for ( int i = 0; i < n/2; i++ ){
        if ( pos[i] == i ) continue;
        if ( inv(pos[i]) < i ){
            cout << "-1\n";
            return;
        }
        if ( inv(i) == pos[i] ){
            rem.pb(i);
            continue;
        }
        answer(i, pos[i]);
    }
    if ( (int)rem.size() & 1 ){
        cout << "-1\n";
        return;
    }
    for ( int i = 1; i < (int)rem.size(); i += 2 ){
        answer(rem[i], inv(rem[i-1]));
        answer(rem[i], rem[i-1]);
    }
    for ( int i = 0; i < n; i++ ){
        if ( pos[i] != i ){
            cout << "-1\n";
            return;
        }
    }
    print();
}
signed main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

    int T; cin >> T;
    while ( T-- ){
        solve();
    }

 	cout << '\n';
}

Compilation message (stderr)

cat.cpp: In function 'void IO(std::string)':
cat.cpp:11:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   11 | void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cat.cpp:11:70: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   11 | void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                                                               ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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