[HNOI2012]永无乡

#include<bits/stdc++.h>
#define MAXN 600005
using namespace std;
int n,m,fa[MAXN],date,q;
int num[MAXN],ch[MAXN][2],sz[MAXN],f[MAXN],cnt[MAXN],tot,zhuan[MAXN];

inline int read()
{
    register int x=0,t=1;
    register char ch=getchar();
    while(ch!='-'&&(ch<'0'||ch>'9'))ch=getchar();
    if(ch=='-'){t=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-48;ch=getchar();}
    return x*t;
}

struct Splay{
    int rt;
    int get(int x){
        return (x==ch[f[x]][1]);
    }
    int up(int x){
        sz[x] = cnt[x];
        if(ch[x][0])sz[x] = sz[x]+sz[ch[x][0]];
        if(ch[x][1])sz[x] = sz[x]+sz[ch[x][1]];
        return 0;
    }
    int rote(int x){
        int y = f[x],z = f[y],k = get(x),p = get(y);
        if(y==0)return 0;
        if(z)ch[z][p] = x;
        if(ch[x][k^1])f[ch[x][k^1]] = y;
        ch[y][k] = ch[x][k^1];
        ch[x][k^1] = y;
        f[x] = z;
        f[y] = x;
        up(y);up(x);
        return 0;
    }
    int splay(int x){
        for(int y = f[x];(y = f[x]);rote(x)){
            rote((get(x)==get(y))?y:x);
        }
        rt = x;
        return 0;
    }
    int rank(int x){
        int now=rt,ans=1;
        while(1){
            if(num[now]<=x){
                ans =     ans+sz[ch[now][0]];
                if(num[now]==x){
                splay(now);
                return ans;
                }
                ans = ans+cnt[now];
                now = ch[now][1];
            }
            else{
                now = ch[now][0];
            }
        }
    }
    int pre(){//前继 比她小的最大 
        int now = ch[rt][0];
        while(ch[now][1])now = ch[now][1];
        return now;
    }
    int suc(){
        int now = ch[rt][1];
        while(ch[now][0])now = ch[now][0];
        return now;
    }
    int add(int x,int js){
        if(rt == 0){
            tot++;
            zhuan[tot] = js;
            num[tot] = x;
            cnt[tot] = 1;
            sz[tot] = 1;
            rt = tot;
            return 0;
        }
        int now = rt;
        while(1){
            if(num[now]==x){
                cnt[now]++;
                splay(now);
                return 0;
            }
            int to = (num[now]<x);
            if(!ch[now][to]){
                tot++;
                zhuan[tot] = js;
                ch[now][to] = tot;
                num[tot] = x;
                f[tot] = now;
                cnt[tot] = 1;
                sz[tot] = 1;
                splay(tot);
                return 0;
            }
            else now = ch[now][to];
        }
    }
    int kth(int x){
        int now =rt;
        while(1){
            if(now==0)return (-1);
            if(sz[ch[now][0]]<x){
                x = x-sz[ch[now][0]];
                if(x<=cnt[now])return zhuan[now];
                x = x-cnt[now];
                now = ch[now][1];
            }
            else{
                now = ch[now][0];
            }
        }
    }
    int del(int x){
        rank(x);
        if(cnt[rt]>=2){
            cnt[rt]--;
            sz[rt]--;
            return 0;
        }
        else{
            if((!ch[rt][0])&&(!ch[rt][1])){
                rt = 0;
                return 0;
            }
            if(ch[rt][0]&&(!ch[rt][1])){
                f[ch[rt][0]] = 0;
                rt =ch[rt][0];
                return 0;
            }
            if((!ch[rt][0])&&ch[rt][1]){
                f[ch[rt][1]] = 0;
                rt =ch[rt][1];
                return 0;
            }
            else{
                splay(pre());
                ch[rt][1] = ch[ch[rt][1]][1];
                f[ch[rt][1]] = rt;
                up(rt);
                return 0;
            }
        }
    }
}T[MAXN];

int mix(int zhu,int fu,int now){//主树编号 副树编号 副树的当前节点 
    if(ch[now][0])mix(zhu,fu,ch[now][0]);
    T[zhu].add(num[now],zhuan[now]);
    if(ch[now][1])mix(zhu,fu,ch[now][1]);
}

int found(int x){
    if(fa[x]==x){
        return x;
    }
    fa[x] = found(fa[x]);
    return fa[x];
}

int main(){
    n = read();
    m = read();
    for(int i=1;i<=n;i++){
    date = read();
    fa[i] = i;
    T[i].add(date,i);
    }
    for(int i=1;i<=m;i++){
        int from,to;
        from = read();
        to = read();
        if(found(from)!=found(to)){//from跟to合并,其中to作为主树 
            mix(found(to),found(from),T[found(from)].rt);
            fa[found(from)] = found(to);
        }
    }
    cin>>q;
    for(int i=1;i<=q;i++){
        char tp;
        int x,y;
        cin>>tp;
        x = read();
        y = read(); 
        if(tp=='B'){
            if(found(x)!=found(y)){//from跟to合并,其中to作为主树 
                mix(found(y),found(x),T[found(x)].rt);
                fa[found(x)] = found(y);
            }    
        }
        else{
            printf("%d
",T[found(x)].kth(y));
        }
    }
}

一道很好的splay合并(暴力)模板题