hdu 3072 Intelligence System

#include <algorithm>
#include <ctype.h>
#include <cstring>
#include <cstdio>
#define N 100005
#define INF 0x7fffffff

using namespace std;
struct graph
{
    graph * next;
    int to,dis;
}Graph[N<<2],*head[N];
inline void Read(int &x)
{
    register char ch=getchar();
    for(x=0;!isdigit(ch);ch=getchar());
    for(;isdigit(ch);x=x*10+ch-‘0‘,ch=getchar());
}
bool instack[N];
int cost[N],cnt,n,m,low[N],dfn[N],stack[N],top,sumcol,col[N],tim;
int min(int a,int b) {return a>b?b:a;}
void tarjan(int now)
{
    dfn[now]=low[now]=++tim;
    instack[now]=true;
    stack[++top]=now;
    for(graph * u=head[now];u;u=u->next)
    {
        int v=u->to;
        if(!dfn[v]) tarjan(v),low[now]=min(low[now],low[v]);
        else if(instack[v]) low[now]=min(low[now],dfn[v]);
    }
    if(dfn[now]==low[now])
    {
        int k;
        sumcol++;
        do
        {
            k=stack[top--];
            instack[k]=false;
            col[k]=sumcol;
        }while(k!=now);
    }
}
inline void init()
{
    cnt=sumcol=top=tim=0;
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(col,0,sizeof(col));
    memset(head,0,sizeof(head));
    memset(Graph,0,sizeof(Graph));
}
inline void ins(int u,int v,int w)
{
    Graph[++cnt].next=head[u];
    Graph[cnt].to=v;
    Graph[cnt].dis=w;
    head[u]=Graph+cnt;
}
int main()
{
    for(;scanf("%d%d",&n,&m)!=EOF;)
    {
        for(int x,y,z;m--;)
        {
            scanf("%d%d%d",&x,&y,&z);
            ins(x,y,z); 
        }
        for(int i=0;i<n;++i)
        {
            if(!dfn[i]) tarjan(i);
            cost[i]=INF;cost[i+1]=INF;
        }
        for(int i=0;i<n;++i)
        {
            for(graph * u=head[i];u;u=u->next)
            {
                int v=u->to;
                if(col[i]!=col[v]) cost[col[v]]=min(cost[col[v]],u->dis);
            }
        }
        int ans=0;
        for(int i=1;i<=sumcol;++i) if(cost[i]!=INF) ans+=cost[i];
        printf("%d\n",ans);
        init();
    }
    return 0;
}