感觉还是挺好的一个题的，虽说是看的小媛的思路；

题意：判断给出的一些字母的先后顺序，进行拓扑排序，看看是否有序；

思路：用flord判断环还是挺好的，然后拓扑排序判断序列的排序关系；

代码：

#include 
      
        #include 
       
         #include 
        
          #include 
         
           #include 
          
            using namespace std; int n = 0; int m = 0; int map[30][30] = {
    0}; int flag = 0; int huan() {
    for(int i = 0;i < n; ++i) for(int j = 0;j < n; ++j) for(int k = 0;k < n; ++k) if(map[j][i]&&map[i][k])     map[j][k] = 1; for(int i = 0;i < n; ++i) if(map[i][i]) return 1; return 0; } int find(int u) {
    int visit[30] = {
    0}; int in[30] = {
    0}; char ans[30] = {
    0}; for(int i = 0;i < n; ++i) for(int j = 0;j < n; ++j) if(map[i][j])     ++in[j]; int q = 0; for(int i = 0;i < n;++i)     {
    int num = 0; int temp  = 0; for(int j = 0;j < n; ++j) if(!visit[j] && in[j] == 0)         {
                ans[q++] = j + 'A';             ++num;             visit[j] = 1;             temp = j;         } if(num > 1) return 0; for(int k = 0;k < n; ++k) if(map[temp][k])         --in[k];     }     printf("Sorted sequence determined after %d relations: ",u); for(int i = 0;i < q; ++i)     printf("%c",ans[i]);     printf(".\n"); return 1; } int main() {
    while(scanf("%d%d",&n,&m),n&&m)     {
            memset(map,0,sizeof(map)); char str[4] = {NULL};         flag = 0; for(int i  = 1;i <= m; ++i)         {
                scanf("%s",str);             map[str[0]-'A'][str[2]-'A'] = 1; if(flag) continue; if(huan())             {
                    flag = 1;                 printf("Inconsistency found after %d relations.\n",i); continue;             } if(find(i))             {
                    flag = 2; continue;             }         } if(flag == 0)         printf("Sorted sequence cannot be determined.\n");     } }