Submission #668647

#	Time	Username	Problem	Language	Result	Execution time	Memory
668647		finn__	Coins (IOI17_coins)	C++17	100 / 100	9 ms	1556 KiB

coins

#include "coins.h"

std::vector<int> coin_flips(std::vector<int> b, int c)
{
    unsigned const row = c / 8, col = c % 8;
    int u = row ^ 7, v = col ^ 7;

    for (unsigned i = 0; i < 8; i++)
    {
        for (unsigned j = 0; j < 8; j++)
        {
            int const &x = b[i * 8 + j];

            if (!(i & 4))
                u ^= (x << 2);
            if (!(i & 2))
                u ^= (x << 1);
            if (!(i & 1))
                u ^= x;

            if (!(j & 4))
                v ^= (x << 2);
            if (!(j & 2))
                v ^= (x << 1);
            if (!(j & 1))
                v ^= x;
        }
    }

    return {u * 8 + v};
}

int find_coin(std::vector<int> b)
{
    unsigned row = 0, col = 0;

    for (unsigned i = 0; i < 8; i++)
    {
        for (unsigned j = 0; j < 8; j++)
        {
            int const &x = b[i * 8 + j];

            if (!(i & 4))
                row ^= (x << 2);
            if (!(i & 2))
                row ^= (x << 1);
            if (!(i & 1))
                row ^= x;

            if (!(j & 4))
                col ^= (x << 2);
            if (!(j & 2))
                col ^= (x << 1);
            if (!(j & 1))
                col ^= x;
        }
    }

    return row * 8 + col;
}

• Subtask 1: 10 / 10
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 15 / 15
• Subtask 5: 50 / 50