八数码问题，IDA*解~

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 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 
 5  using namespace std;
 6 
 7  const int SIZE = 365000;
 8 const int LEN = 10;
 9 const int move[][5] = {{2,3,1},{3,4,0,2},{2,5,1},{3,6,4,0},{4,7,3,5,1},{3,8,4,2},{2,7,3},{3,6,8,4},{2,7,5}};
10 const char moves[][8] = {"dr","dlr","dl","dru","dlru","dlu","ru","lru","lu"};
11 const int DIST[][LEN] =
12 {
13     {0,1,2,1,2,3,2,3,4},
14     {1,0,1,2,1,2,3,2,3},
15     {2,1,0,3,2,1,4,3,2},
16     {1,2,3,0,1,2,1,2,3},
17     {2,1,2,1,0,1,2,1,2},
18     {3,2,1,2,1,0,3,2,1},
19     {2,3,4,1,2,3,0,1,2},
20     {3,2,3,2,1,2,1,0,1},
21     {4,3,2,3,2,1,2,1,0}
22 };
23 
24 char org[LEN];
25 char des[LEN];
26 
27 char output[SIZE];
28 
29 int maxstep;
30 
31 int Estimate(char * key)
32 {
33     int value = 0;
34     for (int i = 0;i < LEN - 1;i++)
35         if (key[i] != '0')
36             value += DIST[i][strchr(des,key[i])-des];
37     return value;
38 }
39 
40 bool IDAstar(int now,int pos,int pre)
41 {
42     int need = Estimate(org);
43     if (now + need > maxstep) return false;
44 
45     if (need == 0)
46     {
47         printf("%d\n",now);
48         output[now] = '\0';
49         printf("%s\n",output);
50         return true;
51     }
52 
53     for (int i = 1;i <= move[pos][0];i++)
54     {
55         int npos = move[pos][i];
56 
57         if (npos == pre) continue;
58 
59         swap(org[pos],org[npos]);
60         output[now] = moves[pos][i-1];
61         if (IDAstar(now + 1,npos,pos)) return true;
62         swap(org[pos],org[npos]);
63     }
64     return false;
65 }
66 
67 int main()
68 {
69     //freopen("1.in","r",stdin);
70     //freopen("out.txt","w",stdout);
71 
72     int cas;
73     int idx;
74 
75     scanf("%d",&cas);
76 
77     for (int cc = 0;cc < cas;cc++)
78     {
79         scanf("%s",org);
80         for (int i = 0;i < LEN - 1;i++)
81             if (org[i] == 'X')
82             {
83                 idx = i;
84                 org[i] = '0';
85             }
86 
87         scanf("%s",des);
88         for (int i = 0;i < LEN - 1;i++)
89             if (des[i] == 'X')
90                 des[i] = '0';
91 
92         printf("Case %d: ",cc + 1);
93 
94         for (maxstep = Estimate(org);;maxstep++)
95             if (IDAstar(0,idx,-1))
96                 break;
97     }
98     return 0;
99 }