bfs poj2965

TLE了 不知道怎么办 还是用枚举？

// poj 2965  bfs & STL queue
# include <iostream>
# include <cstring>
# include <queue>

using namespace std;

const unsigned short flip[] = {0x111f, 0x222f, 0x444f, 0x888f,
                                   0x11f1, 0x22f2, 0x44f4, 0x88f8,
                                   0x1f11, 0x2f22, 0x4f44, 0x8f88,
                                   0xf111, 0xf222, 0xf444, 0xf888};

unsigned short bfs(unsigned short start);
bool judge(unsigned short start, unsigned short x);

int main()
{
    char board[4][4];
    for (int i=0; i<4; ++i)
        cin >> board[i];
    unsigned short start = 0x0;
    for (int i=0; i<4; ++i)
        for (int j=0; j<4; ++j)
            if (board[i][j]=='+')
                start += 1<<(i*4+j);
    unsigned short ans;
    ans = bfs(start);
    if (ans == 0) cout << 0 << endl;
    else
    {
        int cnt = 0;
        for (int i=0; i<16; ++i)
            if (ans>>i & 0x1) ++cnt;
        cout << cnt << endl;
        for (int i=0; i<16; ++i)
            if (ans>>i & 0x1)
                cout << i/4+1 << ' ' << i%4+1 << endl;
    }
    return 0;
}
unsigned short bfs(unsigned short start)
{
    queue<unsigned short> Q;
    bool vis[1<<16];
    memset(vis, 0, sizeof(vis));
    Q.push(0);
    while (!Q.empty())
    {
        unsigned short x;
        x = Q.front();
        Q.pop();
        vis[x] = true;
        if (judge(start, x))return x;
        for (int i=0; i<16; ++i)
        {
            if ((x>>i) & 0x1) ;
            else if (!vis[x+(1<<i)])
                Q.push(x+(1<<i));
        }
    }
    return 0;
}
bool judge(unsigned short start, unsigned short x)
{
    for (int i=0; i<16; ++i)
        if (x>>i & 0x1) start ^= flip[i];
    if(start == 0) return true;
    else return false;
}