BZOJ3910 火车

先orz小火车IOI rank2……

傻逼我做法：LCT维护链染色和查询单点颜色，链长度

orz commonc做法：以起点为根建树，一个点没被走过的充要条件是他的子树内没有点被作为过行进目标，拿树状数组搞就好了

其实用并查集搞也可以

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<ctime>
#include<algorithm>
#include<iomanip>
#include<cmath>
#include<vector>
#include<set>
#include<bitset>
#include<queue>
#include<stack>
#include<map>
using namespace std;
#define MAXN 500010
#define MAXM 1010
#define eps 1e-8
#define ll long long
#define INF 1000000000
#define MOD 1000000007
#define lb(x) x&-x
struct vec{
int to;
int fro;
};
vec mp[MAXN*2];
int tai[MAXN],cnt;
int n,m,s;
int fa[MAXN][21],dep[MAXN],siz[MAXN],dfn[MAXN],tim;
int c[MAXN];
ll ans;
void change(int x){
for(;x<=n;x+=lb(x)){
c[x]++;
}
}
int ask(int x){
int re=0;
for(;x;x-=lb(x)){
re+=c[x];
}
return re;
}
inline void be(int x,int y){
mp[++cnt].to=y;
mp[cnt].fro=tai[x];
tai[x]=cnt;
}
inline void bde(int x,int y){
be(x,y);
be(y,x);
}
void dfs(int x){
int i,j,y,t;
dfn[x]=++tim;
siz[x]=1;
dep[x]=dep[fa[x][1]]+1;
for(i=tai[x];i;i=mp[i].fro){
y=mp[i].to;
if(!siz[y]){
for(j=1,t=x;t;j++){
fa[y][j]=t;
t=fa[t][j];
}
dfs(y);
siz[x]+=siz[y];
}
}
}
int lca(int x,int y){
int i;
if(dep[x]<dep[y]){
swap(x,y);
}
for(i=20;i;i--){
if(dep[fa[x][i]]>=dep[y]){
x=fa[x][i];
}
}
for(i=20;i;i--){
if(fa[x][i]!=fa[y][i]){
x=fa[x][i];
y=fa[y][i];
}
}
return x==y?x:fa[x][1];
}
int dis(int x,int y){
return dep[x]+dep[y]-2*dep[lca(x,y)];
}
int main(){
/*
freopen("data.txt","r",stdin);
freopen("dui.txt","w",stdout);
//*/
int i,x,y;
scanf("%d%d%d",&n,&m,&s);
for(i=1;i<n;i++){
scanf("%d%d",&x,&y);
bde(x,y);
}
dfs(s);
scanf("%d",&x);
ans+=dis(s,x);
change(dfn[x]);
change(dfn[s]);
s=x;
for(i=2;i<=m;i++){
scanf("%d",&x);
if(!(ask(dfn[x]+siz[x]-1)-ask(dfn[x]-1))){
ans+=dis(s,x);
s=x;
change(dfn[x]);
}
}
printf("%lld\n",ans);
return 0;
}

/*
5 4 2
1 2
2 3
3 4
4 5
4 3 1 5

*/