POJ 1753 (枚举+DFS)

#include<stdio.h>
#include<string.h>
#include<iostream>

#include<stdlib.h>


using namespace std;

#define N  7

bool mat[N][N], flag;
int deep;

int dx[] = {1, -1, 0, 0, 0};
int dy[] = {0, 0, 1, -1, 0};

void Init()
{
    char c;
    for(int i = 1; i <= 4; i++)
    {
        for(int j = 1; j <= 4; j++)
        {
            scanf(" %c",&c);
            if(c == ‘b‘)
            {
                mat[i][j] = 1;
            }
            else
            {
                mat[i][j] = 0;
            }
        }
    }
}
void Print()
{
    for(int i = 1; i <= 4; i++)
    {
        for(int j = 1; j <= 4; j++)
            printf("%d", mat[i][j]);
        printf("\n");
    }
}

void Change(int x, int y)
{
    int next_x, next_y;
    for(int k = 0; k < 5; k++)
    {
        next_x = x + dx[k];
        next_y = y + dy[k];
        //if(next_x >= 1 && next_x <=4 && next_y >= 1 && next_y <=4)
        //{
            mat[next_x][next_y] = !mat[next_x][next_y];
        //}
    }
}
void Flip(int x)
{
    switch(x)   //1~16种case代表4*4的16个格子
    {

        case 1: Change(1,1); break;
        case 2: Change(1,2); break;
        case 3: Change(1,3); break;
        case 4: Change(1,4); break;

        case 5: Change(2,1); break;
        case 6: Change(2,2); break;
        case 7: Change(2,3); break;
        case 8: Change(2,4); break;

        case 9:  Change(3,1); break;
        case 10: Change(3,2); break;
        case 11: Change(3,3); break;
        case 12: Change(3,4); break;

        case 13: Change(4,1); break;
        case 14: Change(4,2); break;
        case 15: Change(4,3); break;
        case 16: Change(4,4); break;
    }
}
bool Result()
{
    for(int i = 1; i <= 4; i++)
    {
        for(int j = 1; j <= 4; j++)
            if(mat[i][j] != mat[1][1])
                return false;
    }
    return true;
}
void Dfs(int x, int dp)
{

    if(flag || dp > deep || x>16) return;
    //printf("DFS(%d, %d)\n", x, dp);

    Flip(x);
    //Print();printf("---------\n");
    if(dp == deep)
    {
        flag = (flag || Result());
        if(flag)
        {
            //printf("OK!!!!!!!!!!!!!!");
            //exit(0);
            goto A;
        }

    }
    Dfs(x+1, dp+1);
    Flip(x);
    //Print();printf("---------\n");
    Dfs(x+1, dp);
    A: return;
}

int main()
{
//每个棋子最多翻一次（其实是奇数次，但是没意义），翻偶数次和没翻一样，所以每个棋子就两种状态，翻或者不翻
//所以一共就有2^16次方种可能，枚举这些可能就行了，DFS
//从0到16，如果16还找不到那就是Impossible
    int a, b;
    Init();
    //Print();

    flag = false;
    if(Result())
    {
        cout<<0<<endl;
        return 0;
    }

    for(deep = 1; deep <= 16; deep++)
    {
        //cout<<"deep = "<<deep<<endl;
        Dfs(1, 1);
        if(flag) break;
    }



    if(flag) cout<<deep<<endl;
    else cout<<"Impossible"<<endl;

//    while(cin>>a)
//    {
//        Flip(a);
//        Print();
//    }

    return 0;
}
/*
bwwb
bbwb
bwwb
bwww

wwww
wwww
wwww
wwww

bbbw
wbww
wwww
wwww

wwww
wwww
wwwb
wwbb

bbww
bwww
wwww
wwww

wwbw
bbww
wwww
wwww
*/