1 #include<stdio.h>
2 #include<string.h>
3 bool map[30][30];
4 int in[30],sort[30];
5 int n,m,t;
6 bool f1,f2;
7 void solve(){
8 int i,j,k,loc;
9 int temp[30];
10 bool f=0;
11 for(i=0;i<n;i++)
12 temp[i]=in[i];
13 for(t=i=0;i<n;i++){
14 for(k=j=0;j<n;j++)
15 if(!temp[j]){
16 k++;
17 loc=j;
18 }
19 if(k==0){
20 f2=1;
21 return;
22 }
23 if(k>1) f=1;
24 sort[t++]=loc;
25 temp[loc]=-1;
26 for(j=0;j<n;j++)
27 if(map[loc][j])
28 temp[j]--;
29
30 }
31 if(!f) f1=1;
32 }
33 int main()
34 {
35 int i,p;
36 char a,b;
37 while(scanf("%d%d",&n,&m),n||m){
38 memset(map,0,sizeof(map));
39 memset(in,0,sizeof(in));
40 for(f1=f2=t=i=0;i<m;i++){
41 scanf("%*c%c<%c",&a,&b);
42 if(!f1&&!f2){
43 map[a-'A'][b-'A']=1;
44 in[b-'A']++;
45 solve();
46 p=i+1;
47 }
48 }
49 if(f1){
50 printf("Sorted sequence determined after %d relations: ",p);
51 for(i=0;i<t;i++)
52 printf("%c",sort[i]+'A');
53 puts(".");
54 }else if(f2){
55 printf("Inconsistency found after %d relations.\n",p);
56
57 }else puts("Sorted sequence cannot be determined.");
58 }
59 return 0;
//一道典型的拓扑排序的题目，纠结了好长时间！！
