链式前向星建图

#include <vector>
using namespace std;
#include<iostream>
#include <cstdio>
#include <cstring>
#define maxn 200005
struct Edge
{
    int v,next;
}edge[maxn];
int head[maxn];
int cnt;
void addedge(int u,int v)
{
    edge[cnt].v=v;
    edge[cnt].next=head[u];
    head[u]=cnt;
    cnt++;
}
int main()
{
    int n,m;
    memset(head,-1,sizeof head);
    cin>>n>>m;
    for(int i=1;i<=m;++i)
    {
        int u,v;
        cin>>u>>v;
        addedge(u,v);
    }
    int x;
    cin>>x;
    for(int i=head[x];i!=-1;i=edge[i].next)
    {
        printf("%d->%d\n",x,edge[i].v);
    }
    return 0;
}