1 #include<iostream>
 2 #include<queue>
 3 using namespace std;
 4
 5 typedef struct
 6 {
 7     int now[4];
 8     int step;
 9 }state;
10 int full[4] = {9 , 7 , 4 , 2};
11 int vis[10][8][5][3];  //用来判断是否是已经记录的状态
12
13 int bfs(state& temp , int i , int j)
14 {
15     if(i == j) return 0;  //i中的水不能倒在i中
16     if(temp.now[i] == 0) return 0;  //i中没有水，不能操作
17     if(temp.now[j] == full[j]) return 0;  //j中水已满，不能操作
18     if(temp.now[i] + temp.now[j] <= full[j])  //进入倒水环节
19     {
20         temp.now[j] = temp.now[j] + temp.now[i];  //将i中的水全部倒入j中   ******
21         temp.now[i] = 0;
22     }
23     else                                  //将j倒满
24     {
25         temp.now[i] = temp.now[i] - (full[j] - temp.now[j]);
26         temp.now[j] = full[j];
27     }
28     if(vis[temp.now[0]][temp.now[1]][temp.now[2]][temp.now[3]])
29     {return 0;}
30     else vis[temp.now[0]][temp.now[1]][temp.now[2]][temp.now[3]] = 1;
31     temp.step++;
32     return 1;
33 }
34 int main()
35 {
36     int end[4];   //需要输入的最后状态
37     int i , j , flag;
38     while(cin>>end[0]>>end[1]>>end[2]>>end[3])
39     {
40         queue<state>q;
41         flag = 0;
42         memset(vis , 0 , sizeof(vis));
43         if(end[0]+end[1]+end[2]+end[3]!=9)  //非法状态
44         {cout<<"-1"<<endl;flag = 1;}
45         if(end[0]>full[0]||end[1]>full[1]||end[2]>full[2]||end[3]>full[3])
46         {cout<<"-1"<<endl;flag = 1;}  //非法状态
47         state star;      //初始状态  初始化
48         star.now[0] = 9;
49         star.now[1] = 0;
50         star.now[2] = 0;
51         star.now[3] = 0;
52         star.step = 0;
53         q.push(star);    //将初始状态压入队列
54         while(!q.empty())
55         {
56             state temp = q.front();
57             q.pop();
58             if(temp.now[0]==end[0]&&temp.now[1]==end[1]&&temp.now[2]==end[2]&&temp.now[3]==end[3])
59             {
60                 flag = 1;
61                 printf("%d\n" , temp.step);
62                 break;
63             }
64             for(i = 0; i < 4; i++)
65             {
66                 for(j = 0; j < 4; j++)
67                 {
68                     state temp2 = temp;
69                     if(bfs(temp2 , i , j))
70                          q.push(temp2);
71                 }
72             }
73         }
74         if(!flag)  cout<<"-1"<<endl;
75     }
76     return 0;
77 }