POJ 1904 King's Quest

 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 = 2000000;
18 struct arc{
19     int to,next;
20 };
21 arc e[maxn];
22 int head[maxn],dfn[maxn],low[maxn],tot;
23 bool instack[maxn];
24 int belong[maxn],cnt,scc,n;
25 stack<int>stk;
26 void add(int u,int v){
27     e[tot].to = v;
28     e[tot].next = head[u];
29     head[u] = tot++;
30 }
31 void tarjan(int u){
32     dfn[u] = low[u] = ++cnt;
33     stk.push(u);
34     instack[u] = true;
35     for(int i = head[u]; i != -1; i = e[i].next){
36         if(!dfn[e[i].to]){
37             tarjan(e[i].to);
38             low[u] = min(low[u],low[e[i].to]);
39         }else if(instack[e[i].to])
40             low[u] = min(low[u],dfn[e[i].to]);
41     }
42     if(dfn[u] == low[u]){
43         int v;
44         scc++;
45         do{
46             v = stk.top();
47             belong[v] = scc;
48             instack[v] = false;
49             stk.pop();
50         }while(v != u);
51     }
52 }
53 vector<int>ans;
54 int main() {
55     int i,j,k,u,v;
56     scanf("%d",&n);
57     for(i = 1; i <= n<<1; i++){
58         dfn[i] = low[i] = belong[i] = 0;
59         instack[i] = false;
60         head[i] = -1;
61     }
62     cnt  = scc = tot = 0;
63     for(i = 1; i <= n; i++){
64         scanf("%d",&k);
65         while(k--){
66             scanf("%d",&j);
67             add(i,j+n);
68         }
69     }
70     for(i = 1; i <= n; i++){
71         scanf("%d",&j);
72         add(j+n,i);
73     }
74     for(i = 1; i <= n; i++)
75         if(!dfn[i]) tarjan(i);
76     for(i = 1; i <= n; i++){
77         ans.clear();
78         for(j = head[i]; j != -1; j = e[j].next){
79             if(e[j].to > n && belong[i] == belong[e[j].to]){
80                 ans.push_back(e[j].to-n);
81             }
82         }
83         sort(ans.begin(),ans.end());//要求递增
84         printf("%d",ans.size());
85         for(j = 0; j < ans.size(); j++)
86             printf(" %d",ans[j]);
87         puts("");
88     }
89     return 0;
90 }