int Q[4] = {1,-1,0,0};
int W[4] = {0,0,1,-1};

void dfs(int x, int y)
{
    //.....
    for (int i = 0; i < 4; i++)
    {
        int a = x + Q[i], b = y + W[i];
        //(a,b) es vecino de (x,y)
        /*
        .
        .
        .
        */
    }
}