poj1753Flip Game【刷题计划】

#include<stdio.h>
#include<string.h>
#define inf 0x3f3f3f3f
int flag,min,map[4][4];
int CheckMap(int map[][4])
{
    for(int i = 0; i < 4; i ++)
        for(int j = 0; j < 4; j ++)
            if(map[i][j] != map[0][0])
            return 0;
    return 1;
}
void Reverse(int ans)
{
    int k[4][2] = {0,1,0,-1,-1,0,1,0};
    int x = ans/4;
    int y = ans%4;
    map[x][y] ^= 1;
    for(int i = 0; i< 4; i ++)
    {
        x = ans/4 + k[i][0];
        y = ans%4 + k[i][1];
        if(x < 0||y < 0||x > 3||y > 3)
            continue;
        map[x][y] ^= 1;
    }
    return;
}
void dfs(int ans,int step)
{
    if(CheckMap(map))
    {
        flag = 1;
        if(step < min)
            min = step;
        return;
    }
    if(ans == 16)
        return;
    dfs(ans+1,step);//不翻转当前棋子 
    Reverse(ans);//翻转当前棋子 
    dfs(ans+1,step+1);//翻转当前棋子步数+1，往下搜索 
    Reverse(ans);    //复原 
}
int main()
{
    
    char str[4][4];
    flag = 0;
    min = inf;
    for(int i = 0; i < 4; i ++)
    {
        for(int j = 0; j < 4; j ++)
        {
            scanf("%c",&str[i][j]);
            if(str[i][j] == ‘b‘)
                map[i][j] = 1;
            else 
                map[i][j] = 0;
        }
        getchar();
    }
    dfs(0,0);
    if(!flag)
        printf("Impossible\n");
    else
        printf("%d\n",min);
    return 0;
}