Tarjan模板题 The Bottom of a Graph

题意：找出所有出度为0的连通分支
AC代码

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
#define CLR(a,b) memset(a,b,sizeof(a))
#define INF 0x3f3f3f3f
#define LL long long
#define Pi acos(-1.0)
#define EXP 1e-9
#define up(i,x,y) for(int i=x;i<=y;i++)
#define down(i,x,y) for(int i=x;i>=y;i--)
#define w(x) while(x)
#define Mod 1000000007
struct node{
    int next;
    int v;
}edge[50100];
int dfn[50100];
int low[50100];
int head[50100];
int astack[50100];
int vis[50100];
int astacknum=0;
int cnt=0;
int tot=0;
int belongs[50100];
int belongsnum=0;
int a[50100];
int b[50100];
int out[50100];

void add(int x,int y)
{
    edge[++cnt].next=head[x];
    edge[cnt].v=y;
    head[x]=cnt;
    return ;
}
void tarjan(int x)
{
    dfn[x]=low[x]=++tot;
    astack[++astacknum]=x;
    vis[x]=1;
    for(int i=head[x];i!=-1;i=edge[i].next){
        if(!dfn[edge[i].v]){
            tarjan(edge[i].v);
            low[x]=min(low[x],low[edge[i].v]);
        }
        else if(vis[edge[i].v])
            low[x]=min(low[x],dfn[edge[i].v]);
    }
    if(low[x]==dfn[x]){
        belongsnum++;
        do{
            belongs[astack[astacknum]]=belongsnum;
            vis[astack[astacknum]]=0;
            astacknum--;
        }while(x!=astack[astacknum+1]);
    }
    return ;
}

void init()
{
    CLR(dfn,0);
    CLR(low,0);
    CLR(out,0);
    cnt=0;
    tot=0;
    CLR(belongs,0);
    belongsnum=0;
    CLR(astack,0);
    astacknum=0;
    CLR(vis,0);
    CLR(head,-1);
    return ;
}
int main()
{
    int v,e;
    while(cin>>v){
        if(v==0)
            break;
        cin>>e;
        init();
        for(int i=1;i<=e;i++){
            cin>>a[i]>>b[i];
            add(a[i],b[i]);
        }
        for(int i=1;i<=v;i++){
            if(!dfn[i]) tarjan(i);

        }

        for(int i=1;i<=e;i++){
            if(belongs[a[i]]!=belongs[b[i]]){
                out[belongs[a[i]]]++;
            }
        }
        int flag=0;
        for(int i=1;i<=v;i++){
            if(out[belongs[i]]==0){
                if(!flag){
                    cout<1;
                }
                else
                    cout<<" "<cout<return 0;
}