Submission #783111

#	Time	Username	Problem	Language	Result	Execution time	Memory
783111		Andrey	Cat (info1cup19_cat)	C++14	100 / 100	463 ms	18660 KiB

cat

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

void solve() {
    int n,a,br = 0,y,b;
    cin >> n;
    vector<int> pos(n+1);
    vector<int> p(n+1);
    vector<pair<int,int>> ans(0);
    for(int i = 1; i <= n; i++) {
        cin >> p[i];
        pos[p[i]] = i;
    }
    for(int i = 1; i <= n/2; i++) {
        if(pos[i] > pos[n-i+1]) {
            br++;
        }
        if(pos[i] != n-pos[n-i+1]+1) {
            cout << -1 << "\n";
            return;
        }
    }
    if(br%2) {
        cout << -1 << "\n";
        return;
    }
    br = 0;
    for(int i = 1; i <= n; i++) {
        y = i;
        while(p[y] != y && p[y] != n-y+1) {
            a = y;
            b = p[y];
            swap(p[a],p[b]);
            ans.push_back({a,b});
            swap(p[n-a+1],p[n-b+1]);
            br++;
        }
    }
    vector<int> idk(0);
    for(int i = 1; i <= n/2; i++) {
        if(p[i] == n-i+1) {
            br++;
            idk.push_back(i);
        }
    }
    for(int i = 0; i < idk.size(); i+=2) {
        ans.push_back({idk[i],n-idk[i+1]+1});
        ans.push_back({idk[i],idk[i+1]});
    }
    cout << br << " " << br << "\n";
    for(int i = 0; i < ans.size(); i++) {
        cout << ans[i].first << " " << ans[i].second << "\n";
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int t;
    cin >> t;
    while(t--) {
        solve();
    }
    return 0;
}

Compilation message (stderr)

cat.cpp: In function 'void solve()':
cat.cpp:46:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |     for(int i = 0; i < idk.size(); i+=2) {
      |                    ~~^~~~~~~~~~~~
cat.cpp:51:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   51 |     for(int i = 0; i < ans.size(); i++) {
      |                    ~~^~~~~~~~~~~~

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