POJ 1236

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 #include <stack>
 6 
 7 using namespace std;
 8 
 9 const int MAX_N = 105;
10 int first[MAX_N],v[MAX_N * MAX_N],Next[MAX_N * MAX_N];
11 int low[MAX_N],pre[MAX_N],cmp[MAX_N];
12 int ind[MAX_N],oud[MAX_N];
13 int N;
14 int dfs_clock,scc_cnt;
15 stack<int > S;
16 
17 
18 void dfs(int u) {
19         low[u] = pre[u] = ++dfs_clock;
20         S.push(u);
21         for(int e = first[u]; e != -1; e = Next[e]) {
22                 if(!pre[ v[e] ]) {
23                         dfs(v[e]);
24                         low[ u] = min(low[u],low[ v[e] ]);
25                 } else {
26                         if(!cmp[ v[e] ]) {
27                                 low[u] = min(low[u],pre[ v[e] ]);
28                         }
29                 }
30         }
31 
32         if(low[u] == pre[u]) {
33                 ++scc_cnt;
34                 for(;;) {
35                         int x = S.top(); S.pop();
36                         cmp[x] = scc_cnt;
37                         if(x == u) break;
38                 }
39         }
40 }
41 void scc() {
42         dfs_clock = scc_cnt = 0;
43         memset(cmp,0,sizeof(cmp));
44         memset(pre,0,sizeof(pre));
45 
46         for(int i = 1; i <= N; ++i)  if(!pre[i]) dfs(i);
47 }
48 
49 void add_edge(int id,int u) {
50         int e = first[u];
51         Next[id] = e;
52         first[u] = id;
53 }
54 
55 void solve() {
56         scc();
57         for(int i = 1; i <= N; ++i) {
58                 for(int e = first[i]; e != -1; e = Next[e]) {
59                         if(cmp[ v[e] ] == cmp[i]) continue;
60                         ind[ cmp[ v[e] ] ]++;
61                         oud[ cmp[i] ]++;
62                 }
63         }
64         int in = 0,ou = 0;
65         for(int i = 1; i <= scc_cnt; ++i) {
66                 if(!ind[i]) in++;
67                 if(!oud[i]) ou++;
68         }
69         printf("%d\n%d\n",in,scc_cnt == 1 ? 0 : max(in,ou));
70 
71 }
72 int main()
73 {
74    //freopen("sw.in","r",stdin);
75 
76     scanf("%d",&N);
77     int len = 0;
78     for(int i = 1; i <= N; ++i) first[i] = -1;
79 
80     for(int i = 1; i <= N; ++i) {
81             int ch;
82             scanf("%d",&ch);
83             while(ch != 0) {
84                    // printf("%d ",ch);
85 
86                     add_edge(len,i);
87                     v[len++] = ch;
88                     scanf("%d",&ch);
89             }
90             //cout << endl;
91     }
92 
93     solve();
94     //cout << "Hello world!" << endl;
95     return 0;
96 }