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])));
        }
    }
}