HDU 3072 图论scc

#include<bits/stdc++.h>
#define INF 0x7fffffff
using namespace std;
const int MAXN = 50010;//点数 
const int MAXM = 100100;//边数 
struct Edge {  
    int to,next,val; 
}edge[MAXM]; 
int head[MAXN],tot,a,b; 
int Low[MAXN],DFN[MAXN],Stack[MAXN],Belong[MAXN];//Belong数组的值是1~scc 
int Index,top; int scc;//强连通分量的个数 
int in[MAXN],out[MAXN],val[MAXN],d[MAXN];
bool Instack[MAXN]; 
int num[MAXN];//各个强连通分量包含点的个数，数组编号1~scc //num数组不一定需要，结合实际情况 
int cnt=0,ans=0;
void addedge(int u,int v,int w){  
    edge[tot].to = v;
    edge[tot].next = head[u];
    edge[tot].val=w;
    head[u] = tot++; 
} 
void Tarjan(int u){
    int v;  
    Low[u] = DFN[u] = ++Index; 
    Stack[top++] = u;  
    Instack[u] = true;  
    for(int i = head[u];i != -1;i = edge[i].next) {  
        v = edge[i].to;   
        if( !DFN[v] ){
            Tarjan(v);   
            if( Low[u] > Low[v] )
                Low[u] = Low[v];   
        }   
        else if(Instack[v] && Low[u] > DFN[v])
            Low[u] = DFN[v];  
        }  
        if(Low[u] == DFN[u]){ 
            scc++; 
            do{    
                v = Stack[--top];
                Instack[v] = false;    
                Belong[v] = scc;    
                num[scc]++;   
            }while( v != u);  
        } 
} 
void find_val(int u){
    int v;
    for(int i = head[u];i != -1;i = edge[i].next){
        v = edge[i].to;
        if(Belong[u]==Belong[v]) continue;
        val[Belong[v]]=min(val[Belong[v]],edge[i].val);
        //out[Belong[u]]++;
    }
}
void solve(int N){
    memset(DFN,0,sizeof(DFN));
    memset(Instack,false,sizeof(Instack));
    memset(num,0,sizeof(num));  
    Index = scc = top = 0;  
    for(int i=1;i<=N;i++) val[i]=INF;
    for(int i = 1;i <= N;i++)
        if(!DFN[i])    
        Tarjan(i); 
    for(int i=1;i<=N;i++){
    //    val[Belong[i]]=min(val[Belong[i]],d[i]);
        find_val(i);
    }
    val[Belong[1]]=0;
    for(int i=1;i<=scc;i++){
        ans+=val[i];
    }
} 
void init(){
    tot = 0; 
    cnt=0,ans=0;
    memset(head,-1,sizeof(head)); 
    memset(in,0,sizeof(in));
    memset(out,0,sizeof(out));
} 
int main(){
    int n,m,u,v,w,T;
    while(scanf("%d%d",&n,&m)!=EOF){ 
        init();
        //for(int i=1;i<=n;i++) scanf("%d",&d[i]);
        for(int i=1;i<=m;i++){
            scanf("%d%d%d",&u,&v,&w);
            u++,v++;
            addedge(u,v,w);    
        }
        solve(n);
        cout<<ans<<endl;
        //cout<<cnt<<' '<<ans<<endl;
    }
    return 0;
}