0401

https://www.luogu.com.cn/problem/P5767

bfs

#include<iostream>
#include<cstring>
#include<queue>
#define R 502
using namespace std;
int g[R][R],a[R],m,n;
char c;
bool vis[R];
struct aa
{
    int d,u;
}q[R];
int bfs(int s)
{
    memset(vis,0,sizeof vis);
    q[0]=(aa){0,s};
    vis[s]=1;
    int head=0,tail=1;
    while(head<tail)
    {
        aa p=q[head++];
        if(p.u==n) return p.d-1;
        int uu=p.u;
        for(int v=1;v<=n;v++)
        {
            if(!vis[v]&&g[uu][v])
            {
                q[tail++]=(aa){p.d+1,v};
                vis[v]=1;
            }
        }
    }
    return -1;
}
int main()
{
     cin>>m>>n;
    while(m--)
    {
        int tmp=1;
        cin>>a[tmp];
        c=getchar();
        while(c==' ')
        {
            tmp++;
            cin>>a[tmp];
               c=getchar();
        }
        for(int i=1;i<=tmp;i++)
        {
            for(int j=i+1;j<=tmp;j++)
            {
                g[a[i]][a[j]]=1;
            }
        }
    }
    int ans=bfs(1);
    if(ans!=-1) cout<<ans<<endl;
    else puts("NO");
    return 0;
}