codevs——1036 商务旅行

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define N 300000
using namespace std;
bool vis[N];
int n,m,x,y,tot,lca,ans;
int a[N],fa[N],deep[N],size[N],top[N],head[N];
int read()
{
    int x=0,f=1; char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1; ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘; ch=getchar();}
    return x*f;
}
struct Edge
{
    int from,to,next;
}edge[N];
int add(int x,int y)
{
    tot++;
    edge[tot].to=y;
    edge[tot].next=head[x];
    head[x]=tot;
}
int dfs(int x)
{
    size[x]=1;vis[x]=true;
    deep[x]=deep[fa[x]]+1;
    for(int i=head[x];i;i=edge[i].next)
    {
        int to=edge[i].to;
        if(fa[x]!=to&&!vis[to])
        {
            fa[to]=x;
            dfs(to);
            size[x]+=size[to];
        }
    }
}
int dfs1(int x)
{
    int t=0; vis[x]=true;
    if(!top[x]) top[x]=x;
    for(int i=head[x];i;i=edge[i].next)
    {
        int to=edge[i].to;
        if(fa[x]!=to&&size[to]>size[t]) t=to;
    }
    if(t&&!vis[t])
    {
        top[t]=top[x];
        dfs1(t);
    }
    for(int i=head[x];i;i=edge[i].next)
    {
        int to=edge[i].to;
        if(fa[x]!=to&&to!=t&&!vis[to])
         dfs1(to);
    }
}
int LCA(int x,int y)
{
    while(top[x]!=top[y])
    {
        if(deep[top[x]]<deep[top[y]])
          swap(x,y);
        x=fa[x];
    }
    if(deep[x]>deep[y])
     swap(x,y);
    return x;
}
int main()
{
    n=read();a[0]=1;
    for(int i=1;i<n;i++) 
     x=read(),y=read(),add(x,y),add(y,x);
    dfs(1);memset(vis,0,sizeof(vis));
    dfs1(1);m=read();//a[1]=read();
    for(int i=1;i<=m;i++)
    {
        a[i]=read();
        lca=LCA(a[i-1],a[i]);
        ans+=deep[a[i-1]]+deep[a[i]]-2*deep[lca];
        //printf("%d %d\n",lca,ans);
    }
    printf("%d",ans);
    return 0;
}