HDU 1827 Summer Holiday(Tarjan缩点）[通俗易懂]

    12 16
2 2 2 2 2 2 2 2 2 2 2 2 
1 3
3 2
2 1
3 4
2 4
3 5
5 4
4 6
6 4
7 4
7 12
7 8
8 7
8 9
10 9
11 10

    3 6
   
   
   
   

   
   
   
   
    
    题意：中文
   
   
   
   
    
     
   
   
   
   
    
    
    
    #include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<limits.h>
typedef long long LL;
using namespace std;
const int INF=0x3f3f3f;

#define REPF( i , a , b ) for ( int i = a ; i <= b ; ++ i )
#define REP( i , n ) for ( int i = 0 ; i < n ; ++ i )
#define CLEAR( a , x ) memset ( a , x , sizeof a )

const int maxn=1100;
const int maxm=10000;
struct node{
    int u,v;
    int next;
}e[maxm];
int head[maxn],cntE;
int DFN[maxn],low[maxn];
int s[maxm],top,index,cnt;
int belong[maxn],instack[maxn];
int in[maxn],val[maxn];
int tt[maxn];//tt保存缩成的点中的最小值
int n,m;
void init()
{
    top=cntE=0;
    index=cnt=0;
    CLEAR(DFN,0);
    CLEAR(head,-1);
    CLEAR(instack,0);
}
void addedge(int u,int v)
{
    e[cntE].u=u;e[cntE].v=v;
    e[cntE].next=head[u];
    head[u]=cntE++;
}
void Tarjan(int u)
{
    DFN[u]=low[u]=++index;
    instack[u]=1;
    s[top++]=u;
    for(int i=head[u];i!=-1;i=e[i].next)
    {
        int v=e[i].v;
        if(!DFN[v])
        {
            Tarjan(v);
            low[u]=min(low[u],low[v]);
        }
        else if(instack[v])
            low[u]=min(low[u],DFN[v]);
    }
    int v;
    if(DFN[u]==low[u])
    {
        cnt++;
        do{
            v=s[--top];
            belong[v]=cnt;
            instack[v]=0;
        }while(u!=v);
    }
}
void work()
{
    REPF(i,1,n)
      if(!DFN[i])  Tarjan(i);
    CLEAR(in,0);
    CLEAR(tt,INF);
    REPF(i,1,n)
    {
        if(tt[belong[i]]>val[i])
            tt[belong[i]]=val[i];
    }
    REPF(k,1,n)
    {
        for(int i=head[k];i!=-1;i=e[i].next)
        {
            int v=e[i].v;
            if(belong[k]!=belong[v])
               in[belong[v]]++;
        }
    }
    int ans=0;
    int num=0;
    REPF(i,1,cnt)
    {
        if(!in[i])
        {
            num++;
            ans+=tt[i];
        }
    }
    printf("%d %d\n",num,ans);
}
int main()
{
    int u,v;
    while(~scanf("%d%d",&n,&m))
    {
        init();
        for(int i=1;i<=n;i++)
            scanf("%d",&val[i]);
        for(int i=0;i<m;i++)
        {
            scanf("%d%d",&u,&v);
            addedge(u,v);
        }
        work();
    }
    return 0;
}