COGS——T 1175. [顾研NOIP] 旅游电车

 1 #include <cstring>
 2 #include <cstdio>
 3 
 4 const int N(5000+15);
 5 const int M(50000+5);
 6 int head[N],sumedge;
 7 struct Edge
 8 {
 9     int v,next;
10     Edge(int v=0,int next=0):v(v),next(next){}
11 }edge[M];
12 inline void ins(int u,int v)
13 {
14     edge[++sumedge]=Edge(v,head[u]);
15     head[u]=sumedge;
16 }
17 
18 #define min(a,b) (a<b?a:b)
19 int tim,dfn[N],low[N];
20 int top,Stack[N],instack[N];
21 int col[N],sumcol,cd[N];
22 void DFS(int u)
23 {
24     low[u]=dfn[u]=++tim;
25     Stack[++top]=u; instack[u]=1;
26     for(int v,i=head[u];i;i=edge[i].next)
27     {
28         v=edge[i].v;
29         if(!dfn[v]) DFS(v), low[u]=min(low[u],low[v]);
30         else if(instack[v]) low[u]=min(low[u],dfn[v]);
31     }
32     if(low[u]==dfn[u])
33     {
34         col[u]=++sumcol;
35         for(;Stack[top]!=u;top--)
36         {
37             instack[Stack[top]]=0;
38             col[Stack[top]]=sumcol;
39         }
40         instack[u]=0; top--;
41     }
42 }
43 
44 inline void init()
45 {
46     sumedge=tim=top=sumcol=0;
47     memset(cd,0,sizeof(cd));
48     memset(low,0,sizeof(low));
49     memset(dfn,0,sizeof(dfn));
50 //    memset(col,0,sizeof(col));
51     memset(edge,0,sizeof(edge));
52     memset(head,0,sizeof(head));
53 //    memset(Stack,0,sizeof(Stack));
54     memset(instack,0,sizeof(instack));
55 }
56 inline void read(int &x)
57 {
58     x=0; register char ch=getchar();
59     for(;ch>‘9‘||ch<‘0‘;) ch=getchar();
60     for(;ch>=‘0‘&&ch<=‘9‘;ch=getchar()) x=x*10+ch-‘0‘;
61 }
62 
63 int AC()
64 {
65     freopen("buss.in","r",stdin);
66     freopen("buss.out","w",stdout);
67     for(int n,m;1;init())
68     {
69         read(n);
70         if(!n) break;
71         read(m);
72         for(int u,v;m--;ins(u,v))
73             read(u),read(v);
74         for(int i=1;i<=n;i++)
75             if(!dfn[i]) DFS(i);
76         for(int v,u=1;u<=n;u++)
77             for(int i=head[u];i;i=edge[i].next)
78             {
79                 v=edge[i].v;
80                 if(col[u]!=col[v]) cd[col[u]]++;
81             }
82         for(int i=1;i<=n;i++)
83             if(!cd[col[i]]) printf("%d ",i);
84         puts("");
85     }
86     return 0;
87 }
88 
89 int Hope=AC();
90 int main(){;}