Submission #1216773

#	Time	Username	Problem	Language	Result	Execution time	Memory
1216773		otarius	Cat (info1cup19_cat)	C++20	25 / 100	224 ms	10892 KiB

cat

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

// #pragma GCC optimize("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#define ff first
#define sc second
#define pb push_back
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define ull unsigned long long
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rngl(chrono::steady_clock::now().time_since_epoch().count());

// #define int long long
// #define int unsigned long long

// #define ordered_set(T) tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>
// #define ordered_multiset(T) tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>

// const ll mod = 1e9 + 7;
// const ll mod = 998244353;

const ll inf = 1e9;
const ll biginf = 1e18;
// const int maxN;

void solve() {
    int n;
    cin >> n;
    int arr[n + 1]; vector<pii> v;
    for (int i = 1; i <= n; i++)
        cin >> arr[i];
    for (int i = 1; i <= n; i++) {
        if (arr[i] + arr[n - i + 1] != n + 1) {
            cout << "-1\n"; return;
        }
    }

    for (int i = 1; i <= n / 2; i++) {
        while (arr[i] != i && arr[i] != n - i + 1) {
            v.pb({i, arr[i]});
            int tmp = arr[i];
            swap(arr[i], arr[tmp]); swap(arr[n - i + 1], arr[n - tmp + 1]);
        }
    }

    // for (int i = 1; i <= n; i++)
    //     cout << arr[i] << ' ';
    // cout << '\n';

    int lst = -1;
    for (int i = 1; i <= n / 2; i++) {
        if (arr[i] == n - i + 1) {
            if (lst == -1) lst = i;
            else {
                v.pb({lst, n - i + 1});
                swap(arr[lst], arr[n - i + 1]);
                swap(arr[n - lst + 1], arr[i]);
                v.pb({lst, i});
                swap(arr[lst], arr[i]);
                swap(arr[n - lst + 1], arr[n - i + 1]);
                lst = -1;
            }
        }
    }

    cout << v.size() << ' ' << v.size() << '\n';
    for (pii x : v) {
        cout << x.ff << ' ' << x.sc << '\n';
    }


}
int32_t main() { 
// #ifndef ONLINE_JUDGE
//     freopen("input.txt", "r", stdin);
//     freopen("output.txt", "w", stdout);
// #endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    
    int t = 1;
    cin >> t;
    while (t--) {
        solve();
        // cout << '\n';
    }
    return 0;
}

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