poj 1753 Flip Game

 1 #include <iostream>
 2 #include <stdio.h>
 3 using namespace std;
 4 bool chess[6][6]= {{false}};
 5 int r[6]= {0,0,0,-1,1};
 6 int c[6]= {0,1,-1,0,0};
 7 int step;
 8 bool flag;
 9 bool reach_all()   //判断是否为一种颜色
10 {
11     for(int i=1;i<5;i++)
12     {
13         for(int j=1;j<5;j++)
14         {
15             if(chess[i][j]!=chess[1][1])
16                 return false;
17         }
18     }
19     return true;
20 }
21 void turn(int row,int col) //翻棋
22 {
23     for(int i=0;i<5;i++)
24         chess[row+r[i]][col+c[i]]=!chess[row+r[i]][col+c[i]];
25     return ;
26 }
27 void dfs(int row,int col,int deep) //  深搜迭代回溯很重要
28 {
29     if(deep==step)
30     {
31         flag=reach_all();
32         return ;
33     }
34     if(flag||row==5)
35         return ;
36     turn(row,col); //翻棋
37     if(col<4)
38         dfs(row,col+1,deep+1);
39     else
40         dfs(row+1,1,deep+1);
41     turn(row,col);  //不符合则翻回来
42     if(col<4)
43         dfs(row,col+1,deep);
44     else
45         dfs(row+1,1,deep);
46     return ;
47 }
48 int main()
49 {
50     char ch;
51     for(int i=1; i<5; i++)
52     {
53         for(int j=1; j<5; j++)
54         {
55             scanf("%c",&ch);
56             if(ch==‘b‘)
57                 chess[i][j]=true;
58         }
59         getchar();   //之前忘了写，就一直输出Impossible
60     }
61     for(step=0; step<=16; step++) //枚举每一种情况
62     {
63         dfs(1,1,0);
64         if(flag)
65             break;
66     }
67     if(flag)
68         printf("%d\n",step);
69     else
70         printf("Impossible\n");
71     return 0;
72 }