1 #include<cstdio> 2 #include<string> 3 #include<iostream> 4 #include<cstring> 5 using namespace std; 6 7 int bian[100][100], vis[100]; 8 void cont (char a, char b, char c, char d) 9 { 10 if(b == '0' || d == '0') 11 return; 12 int l1 = (a - 'A') * 2 + (b == '+'? 0 : 1); 13 int l2 = (c - 'A') * 2 + (d == '+'? 0 : 1); 14 int u = l1 ^ 1; 15 int v = l2; 16 bian[u][v] = 1; 17 } 18 bool bfs(int i) 19 { 20 vis[i] = -1; 21 for(int j = 0; j < 52; j++) 22 if(bian[i][j]) 23 { 24 if(vis[j] < 0) 25 return true; 26 else if( !vis[j] && bfs(j)) 27 return true; 28 } 29 vis[i] = 1; 30 return false; 31 } 32 int main() 33 { 34 int n; 35 while(scanf("%d", &n) != EOF && n) 36 { 37 memset(bian, 0, sizeof(bian)); 38 memset(vis, 0, sizeof(vis)); 39 int flag = 1; 40 while(n--) 41 { 42 string s; 43 cin >> s; 44 for(int i = 0; i < 4; i++) 45 for(int j = 0; j < 4; j++) 46 if(i != j) 47 { 48 cont(s[2*i], s[2*i+1], s[2*j], s[2*j+1]); 49 } 50 } 51 for(int i = 0; i < 52; i++) 52 if(!vis[i]) 53 if(bfs(i)) 54 { 55 flag = 0; 56 break; 57 } 58 if(flag) 59 printf("bounded "); 60 if(!flag) 61 printf("unbounded "); 62 63 } 64 65 }
这是一道关于拓扑排序的题。。。通过这道题，，更深的理解了判断是否为有向环的方法。。。感觉在构建路线时的思维实在是巧妙。。。。了解了^的用法