bzoj1589[Usaco2008 Dec]Trick or Treat on the Farm 采集糖果*

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <stack>
 5 #define inc(i,j,k) for(int i=j;i<=k;i++)
 6 #define maxn 100010
 7 #define ll long long
 8 using namespace std;
 9 
10 inline int read(){
11     char ch=getchar(); int f=1,x=0;
12     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1; ch=getchar();}
13     while(ch>=‘0‘&&ch<=‘9‘)x=x*10+ch-‘0‘,ch=getchar();
14     return f*x;
15 }
16 struct e{int f,t,n;}es[maxn]; int g[maxn],ess,n;
17 void pe(int f,int t){es[++ess]=(e){f,t,g[f]}; g[f]=ess;}
18 bool vis[maxn]; int bel[maxn],sm[maxn],tim,pre[maxn],low[maxn],tot,ins[maxn]; stack<int>st;
19 void dfs1(int x){
20     vis[x]=ins[x]=1; st.push(x); low[x]=pre[x]=++tim;
21     for(int i=g[x];i;i=es[i].n)
22         if(!vis[es[i].t])dfs1(es[i].t),low[x]=min(low[x],low[es[i].t]);
23         else if(ins[es[i].t])low[x]=min(low[x],pre[es[i].t]);
24     if(low[x]==pre[x]){
25         tot++;
26         while(!st.empty()){
27             int now=st.top(); st.pop(); bel[now]=tot; sm[tot]++; ins[now]=0; if(now==x)break;
28         }
29     }
30 }
31 void dfs2(int x){
32     for(int i=g[x];i;i=es[i].n){
33         if(!vis[es[i].t])vis[es[i].t]=1,dfs2(es[i].t),sm[x]+=sm[es[i].t];else sm[x]+=sm[es[i].t];
34     }
35 }
36 int main(){
37     n=read(); inc(i,1,n){int x=read(); pe(i,x);} inc(i,1,n)if(!vis[i])dfs1(i);
38     int m=ess; ess=0; memset(g,0,sizeof(g));
39     inc(i,1,m)if(bel[es[i].f]!=bel[es[i].t])pe(bel[es[i].f],bel[es[i].t]);
40     memset(vis,0,sizeof(vis)); inc(i,1,tot)if(!vis[i])vis[i]=1,dfs2(i);
41     inc(i,1,n)printf("%d\n",sm[bel[i]]); return 0;
42 }