P2661 信息传递

P2661 信息传递
dfs求最小环，要加时间戳，记录这个点是哪一次被dfs到的。]

 #include<iostream>
 #include<cstdio>
 #include<queue>
 #include<algorithm>
 #include<cmath>
 #include<ctime>
 #include<set>
 #include<map>
 #include<stack>
 #include<cstring>
 #define inf 2147483647
 #define For(i,a,b) for(register int i=a;i<=b;i++)
 #define p(a) putchar(a)
 #define g() getchar()
 //by war
 //2017.11.5
 using namespace std;
 int n;
 bool vis[];
 int x;
 int ans;
 int d[];
 int t[];
 struct node
 {
     int n;
     node *next;
 }*e[];
 void in(int &x)
 {
     int y=;
     char c=g();x=;
     while(c<''||c>'')
     {
     if(c=='-')
     y=-;
     c=g();
     }
     while(c<=''&&c>='')x=(x<<)+(x<<)+c-'',c=g();
     x*=y;
 }
 void o(int x)
 {
     if(x<)
     {
         p('-');
         x=-x;
     }
     if(x>)o(x/);
     p(x%+'');
 }

 void push(int x,int y)
 {
     node *p;
     p=new node();
     p->n=y;
     if(e[x]==NULL)
     e[x]=p;
     else
     {
         p->next=e[x]->next;
         e[x]->next=p;
     }
 }

 void dfs(int now,int dis,int Time)
 {
     d[now]=dis;
     vis[now]=true;
     t[now]=Time;
     for(node *i=e[now];i!=NULL;i=i->next)
     if(vis[i->n])
     {
     if(t[now]==t[i->n])
     ans=min(ans,d[now]-d[i->n]+);
     }
     else
     dfs(i->n,dis+,Time);
 }

 int main()
 {
     in(n);
     For(i,,n)
     {
         in(x);
         push(i,x);
     }
     ans=inf;
     For(i,,n)
     {
         if(!vis[i])
         {
         t[i]=i;
         dfs(i,,i);
         }
     }
     o(ans);
      return ;
 }