P4271 [USACO18FEB]New Barns

题目

P4271 [USACO18FEB]New Barns

做法

这题很长见识啊！！

知识点：两棵树\((A,B)\)联通后，新树的径端点为\(A\)的径端点与\(B\)的径端点的两点

不断加边，那就\(LCT\)维护联通块径端点就好了，两点的简单路径就是把链拉起来的子树

My complete code

#include<cstdio>
#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
using namespace std;
typedef int LL;
const LL maxn=1e6;
inline LL Read(){
	LL x(0),f(1);char c=getchar();
	while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}
	while(c>='0'&&c<='9')x=(x<<3)+(x<<1)+c-'0',c=getchar();
	return x*f;
}
LL m,tot;
LL son[maxn][2],fa[maxn],size[maxn],f[maxn],le[maxn],re[maxn],r[maxn],sta[maxn];
inline void Update(LL x){
	size[x]=size[son[x][0]]+size[son[x][1]]+1;
}
inline bool Notroot(LL x){
	return son[fa[x]][0]==x||son[fa[x]][1]==x;
}
inline void Pushr(LL x){
	swap(son[x][0],son[x][1]),r[x]^=1;
}
inline void Pushdown(LL x){
	if(r[x]){
		if(son[x][0]) Pushr(son[x][0]);
		if(son[x][1]) Pushr(son[x][1]);
		r[x]=0;
	}
}
inline void Rotate(LL x){
	LL y(fa[x]),z(fa[y]),lz=(son[y][1]==x);
	if(Notroot(y)) son[z][son[z][1]==y]=x; fa[x]=z;
    son[y][lz]=son[x][lz^1];
    if(son[y][lz]) fa[son[y][lz]]=y;
    son[x][lz^1]=y; fa[y]=x;
    Update(y),Update(x);
}
inline void Splay(LL x){
	LL y(x),top(0);
	sta[++top]=y;
	while(Notroot(y)) sta[++top]=y=fa[y];
	while(top) Pushdown(sta[top--]);
	while(Notroot(x)){
		y=fa[x];
		if(Notroot(y)){
			LL z(fa[y]);
			if(((son[y][1]==x)^(son[z][1]==y))==0) Rotate(y);
			else Rotate(x);
		}Rotate(x);
	}
}
inline void Access(LL x){
	for(LL y=0;x;y=x,x=fa[x])
		Splay(x),son[x][1]=y,Update(x);
}
inline void Makeroot(LL x){
	Access(x),Splay(x),Pushr(x);
}
inline void Split(LL x,LL y){
	Makeroot(x),Access(y),Splay(y);
}
inline void Link(LL x,LL y){
	Makeroot(x),fa[x]=y;
}
inline LL Get_dis(LL x,LL y){
	Split(x,y); return size[y]-1;
}

LL Get_fa(LL x){
	return f[x]=(f[x]==x?x:Get_fa(f[x]));
}
int main(){
	m=Read();
	while(m--){
		char ch; scanf(" %c",&ch);
		if(ch=='B'){
			++tot, size[tot]=1;
			LL x(Read());
			if(x==-1)
			    f[tot]=le[tot]=re[tot]=tot;
			else{
				Link(tot,x); f[tot]=x=Get_fa(x);
				LL l1(Get_dis(le[x],tot)),l2(Get_dis(re[x],tot)),l3(Get_dis(le[x],re[x]));
				if(l1>l2&&l1>l3)
				    re[x]=tot;
				else if(l2>l3)
				    le[x]=tot;
			}
		}else{
			LL x(Read()),fx=Get_fa(x);
			printf("%d\n",max(Get_dis(x,le[fx]),Get_dis(x,re[fx])));
		}
	}
}