指针版邻接表

比起数组优点有三：

1.代码量少

2.fch再也不用想着清-1，不用纠结反向弧

3.更好理解了

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<algorithm>
 5 #include<queue>
 6 #include<cstring>
 7 #define PAU putchar(‘ ‘)
 8 #define ENT putchar(‘\n‘)
 9 using namespace std;
10 const int maxn=100000+10,maxm=100000+10,inf=-1u>>1;
11 struct BFS{
12     struct ted{int x,y;ted*next;}adj[maxm],*fch[maxn],*ms;
13     bool vis[maxn];int n;
14     void init(int n){
15         this->n=n;ms=adj;memset(vis,false,sizeof(vis));return;
16     }
17     void ade(int u,int v){*ms=(ted){u,v,fch[u]};fch[u]=ms++;return;}
18     void bfs(int x){
19         queue<int>Q;Q.push(x);vis[x]=true;
20         while(!Q.empty()){
21             int u=Q.front();Q.pop();
22             for(ted*e=fch[u];e;e=e->next){
23                 int v=e->y;if(!vis[v]) vis[v]=true,Q.push(v);
24             }
25         } return;
26     }
27 }p1,p2;
28 inline int read(){
29     int x=0,sig=1;char ch=getchar();
30     while(!isdigit(ch)){if(ch==‘-‘)sig=-1;ch=getchar();}
31     while(isdigit(ch))x=10*x+ch-‘0‘,ch=getchar();
32     return x*=sig;
33 }
34 inline void write(int x){
35     if(x==0){putchar(‘0‘);return;}if(x<0)putchar(‘-‘),x=-x;
36     int len=0,buf[15];while(x)buf[len++]=x%10,x/=10;
37     for(int i=len-1;i>=0;i--)putchar(buf[i]+‘0‘);return;
38 }
39 int n,m;
40 void init(){
41     n=read();m=read();
42     p1.init(n);p2.init(n);
43     int x,y;
44     for(int i=1;i<=m;i++){
45         x=read();y=read();
46         p1.ade(x,y);
47         p2.ade(y,x);
48     } p1.bfs(1);p2.bfs(1);
49     for(int i=1;i<=n;i++){
50         if(p1.vis[i]&&p2.vis[i]) write(i),ENT;
51     }
52     return;
53 }
54 void work(){
55     return;
56 }
57 void print(){
58     return;
59 }
60 int main(){init();work();print();return 0;}