poj 2965

枚举：位运算版。

谢谢大牛们指导！

# include <iostream>

using namespace std;

const unsigned short int A[] = {0x111f, 0x222f, 0x444f, 0x888f,

                                0x11f1, 0x22f2, 0x44f4, 0x88f8,

                                0x1f11, 0x2f22, 0x4f44, 0x8f88,

                                0xf111, 0xf222, 0xf444, 0xf888

                               };

void Bitflip(unsigned short int * x, size_t h)

{

    size_t i = 0;

    for (; i < 16; ++i)

        if (h>>i & 0x1)

            *x ^= A[i];

}

size_t Bitcount(size_t i)

{

    size_t count = 0, j = 0;

    for (; j < 16; ++j)

        if (i>>j & 0x1) ++count;

    return count;

}

int main()

{

    char handle[4][4];

    unsigned short int h = 0x0, x, ans = 0;

    size_t i = 0, min = 17, c;



    for (i = 0; i < 4; ++i) cin >> handle[i];

    for (int j = 15; j >= 0; --j)

    {

        h <<= 1;

        if (handle[j/4][j%4] == '+')

            h |= 0x1;

    }

    for (i = 0; i <= 65535; ++i)

    {

        if ((c=Bitcount(i)) > min) continue;

        x = h;

        Bitflip(&x, i);

        if (x == 0)

        {

            min = c;

            ans = i;

        }

    }

    cout << min << endl;

    for (i = 0; i < 16; ++i)

        if (ans>>i & 0x1)

            cout <<i/4+1 << " " <<i%4+1 << endl;



    return 0;

}