Submission #634024

#	Time	Username	Problem	Language	Result	Execution time	Memory
634024		boris_mihov	Cat (info1cup19_cat)	C++17	33.75 / 100	413 ms	28156 KiB

cat

#include <algorithm>
#include <iostream>
#include <numeric>
#include <vector>

typedef long long llong;
const int MAXN = 100000 + 10;
const int INF  = 1e9;

int n, m;
int a[MAXN];
int posOf[MAXN];
std::vector < std::pair <int,int> > ops;
inline void operation(int x, int y)
{
    std::swap(a[x], a[y]);
    std::swap(a[n-x+1], a[n-y+1]);
    posOf[a[x]] = x;
    posOf[a[y]] = y;
    posOf[a[n-x+1]] = n-x+1;
    posOf[a[n-y+1]] = n-y+1;
    ops.emplace_back(x, y);
}

void solve()
{
    int cnt = 0;
    ops.clear();
    for (int i = 1 ; i <= n ; ++i)
    {
        if (a[n - i + 1] != n - a[i] + 1)
        {
            std::cout << -1 << '\n';
            return;
        }

        posOf[a[i]] = i;
        if (i <= n/2)
        {
            cnt += (a[i] > n/2);
        }
    }

    if (cnt & 1)
    {
        std::cout << -1 << '\n';
        return;
    }

    for (int i = 1 ; i <= n/2 ; ++i)
    {
        if (a[i] <= n/2) continue;
        int wantedSwap = n-a[i]+1;
        if (i != wantedSwap && a[wantedSwap] > n/2)
        {
            operation(i, n - wantedSwap + 1);
        }
    }

    int lastBig = 0;
    for (int i = 1 ; i <= n/2 ; ++i)
    {
        if (a[i] <= n/2) continue;
        if (lastBig != 0)
        {
            operation(i, n - lastBig + 1);
            lastBig = 0;
        } else
        {
            lastBig = i;
        }
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        if (posOf[i] != i)
        {
            operation(i, posOf[i]);
        }
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        if (a[i] != i)
        {
            std::cout << -1 << '\n';
            return;
        }
    }

    std::cout << ops.size() << ' ' << ops.size() << '\n';
    for (auto [x, y] : ops)
    {
        std::cout << x << ' ' << y << '\n';
    }
}

void read()
{
    std::cin >> n;
    for (int i = 1 ; i <= n ; ++i)
    {
        std::cin >> a[i];
    }
}

void fastIO()
{
    std::ios_base :: sync_with_stdio(0);
    std::cout.tie(nullptr);
    std::cin.tie(nullptr);
}

int tests;
int main()
{
    fastIO();
    std::cin >> tests;
    
    while (tests--)
    {
        read();
        solve();
    }

    return 0;
}

• Subtask 1: 15 / 15
• Subtask 2: 10 / 10
• Subtask 3: 8.75 / 25
• Subtask 4: 0 / 15
• Subtask 5: 0 / 35