POJ1094-Solve All It Out 

 1 #include<iostream>
 2 #include<fstream>
 3 #include<cstring>
 4 
 5 using namespace std;
 6 #define MAXN 28
 7 
 8 bool adj[MAXN][MAXN];
 9 int indegree[MAXN];
10 char str[MAXN];
11 int n, m;
12 
13 
14 
15 
16 int topo_sort()
17 {
18     int i,j,k;
19     int flag = true;
20     memset(indegree,0,sizeof(indegree));
21     memset(str,'\0',sizeof(str));
22     for(i=1; i<=n; i++)
23     {
24         for(j=1; j<=n; j++)
25             if(adj[i][j])
26                 indegree[j]++;
27     }
28     for(i=1; i<=n; i++)
29     {
30         k = 0;
31         for(j=1; j<=n; j++)
32         {
33             if(indegree[j]==0)
34             {
35                 if(k==0) k = j;
36                 else flag = false;
37             }
38         }
39         if(k==0) return 0;
40         indegree[k] = -1;
41         str[i-1] = k+'A'-1;
42         for(j=1; j<=n; j++)
43         {
44             if(adj[k][j])
45                 indegree[j]--;
46         }
47     }
48 
49     if(flag) return 1;
50     else return 2;
51 }
52 
53 int main()
54 {
55 
56     int i, a, b, result;
57     char s[4];
58     while (scanf("%d %d", &n, &m),m+n)  
59     {
60        memset(adj,false,sizeof(adj));
61         bool h=false;
62         for(i=1; i<=m; i++)
63         {
64             scanf("%s", s);
65             a = s[0]-'A'+1;
66             b = s[2]-'A'+1;
67             adj[a][b] = true;
68             if(h) continue;
69             result = topo_sort();
70             if(result == 1)
71             {
72                 printf("Sorted sequence determined after %d relations: %s.\n",i,str);
73                 h = true;
74             }
75             if(result == 0)
76             {
77                 printf("Inconsistency found after %d relations.\n",i);
78                 h = true;
79             }
80         }
81         if(!h)
82             printf("Sorted sequence cannot be determined.\n");
83     }
84     
85     return 0;
86 }

 

posted @ 2013-01-07 19:53  wonderlily  阅读(183)  评论(0)    收藏  举报