POJ 1094 Sorting It All Out

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 105;
18 int n,m,cnt,in[maxn],tmp[maxn],result[maxn];
19 vector<int>g[maxn];
20 queue<int>q;
21 void init() {
22     for(int i = 0; i < maxn; i++) {
23         in[i] = 0;
24         g[i].clear();
25     }
26 }
27 bool Find(int x,int y) {
28     for(int i = 0; i < g[x].size(); i++)
29         if(g[x][i] == y) return false;
30     return true;
31 }
32 int topSort() {
33     while(!q.empty()) q.pop();
34     for(int i = 0; i < n; i++)
35         if(!in[i]) q.push(i);
36     cnt = 0;
37     bool uncertain = false;
38     while(!q.empty()) {
39         int u = q.front();
40         if(q.size() > 1) uncertain = true;
41         q.pop();
42         result[cnt++] = u;
43         for(int i = 0; i < g[u].size(); i++) {
44             if(--in[g[u][i]] == 0) q.push(g[u][i]);
45         }
46     }
47     if(cnt < n) return 1;
48     if(uncertain) return 2;
49     return 3;
50 }
51 int main() {
52     bool ok;
53     char u,v,op;
54     int endPoint,flag;
55     while(scanf("%d %d",&n,&m),n||m) {
56         init();
57         ok = false;
58         getchar();
59         flag = 2;
60         for(int i = 1; i <= m; i++) {
61             scanf("%c%c%c%*c",&u,&op,&v);
62             if(ok) continue;
63             if(op == ‘<‘ && Find(v-‘A‘,u-‘A‘)) {
64                 g[v-‘A‘].push_back(u-‘A‘);
65                 in[u-‘A‘]++;
66             } else if(op == ‘>‘ && Find(u-‘A‘,v-‘A‘)) {
67                 g[u-‘A‘].push_back(v-‘A‘);
68                 in[v-‘A‘]++;
69             }
70             memcpy(tmp,in,sizeof(in));
71             flag = topSort();
72             if(flag != 2) {
73                 endPoint = i;
74                 ok = true;
75             }
76             memcpy(in,tmp,sizeof(in));
77         }
78         if(flag == 3) {
79             printf("Sorted sequence determined after %d relations: ", endPoint);
80             for(int i = cnt-1; i >= 0; i--)
81                 printf("%c",result[i]+‘A‘);
82             puts(".");
83         } else if(flag == 1) printf("Inconsistency found after %d relations.\n",endPoint);
84         else puts("Sorted sequence cannot be determined.");
85     }
86     return 0;
87 }