Submission #743725

#	Time	Username	Problem	Language	Result	Execution time	Memory
743725		borisAngelov	Xor Sort (eJOI20_xorsort)	C++17	100 / 100	8 ms	1028 KiB

xorsort

#include <iostream>
#include <vector>

using namespace std;

const int maxn = 1005;

int n, s;

int a[maxn];

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

int main()
{
    fastIO();

    cin >> n >> s;

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

    vector<pair<int, int>> ans;

    if (s == 1)
    {
        int last = 0;

        for (int i = n; i > 1; --i)
        {
            int idx = 1;

            for (int j = 1; j <= i; ++j)
            {
                if ((a[j] ^ last) > (a[idx] ^ last))
                {
                    idx = j;
                }
            }

            for (int j = 1; j <= i; ++j)
            {
                if (j != n)
                {
                    ans.push_back(make_pair(j, j + 1));
                    a[j] = (a[j] ^ a[j + 1]);
                }
            }

            for (int j = idx + 1; j <= i; ++j)
            {
                ans.push_back(make_pair(j, j - 1));
                a[j] = (a[j] ^ a[j - 1]);
            }

            for (int j = idx - 1; j > 1; --j)
            {
                ans.push_back(make_pair(j - 1, j));
                a[j - 1] = (a[j - 1] ^ a[j]);
            }

            /*for (int j = 1; j <= n; ++j)
            {
                cout << a[j] << ' ';
            }

            cout << endl;*/

            last = a[i];
        }

        ans.push_back(make_pair(1, 2));

        a[1] = (a[1] ^ a[2]);
    }
    else
    {
        for (int bit = 19; bit >= 0; --bit)
        {
            for (int i = 1; i < n; ++i)
            {
                if (((a[i] & (1 << bit)) != 0) && ((a[i + 1] & (1 << bit)) == 0))
                {
                    a[i + 1] = (a[i] ^ a[i + 1]);
                    ans.push_back(make_pair(i + 1, i));
                }

                if (((a[i] & (1 << bit)) != 0) && ((a[i + 1] ^ a[i]) < a[i]))
                {
                    a[i] = (a[i] ^ a[i + 1]);
                    ans.push_back(make_pair(i, i + 1));
                }
            }
        }
    }

    /*for (int i = 1; i <= n; ++i)
    {
        cout << a[i] << ' ';
    }

    cout << endl;*/

    cout << ans.size() << endl;

    for (auto [x, y] : ans)
    {
        cout << x << ' ' << y << "\n";
    }

    return 0;
}

• Subtask 1: 25 / 25
• Subtask 2: 35 / 35
• Subtask 3: 40 / 40