[BZOJ3224]Tyvj 1728 普通平衡树 && treap

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
#include<queue>
#define SF scanf
#define PF printf
using namespace std;
typedef long long LL;
inline int read() {
    int x=0, f=1; char ch=getchar();
    while(ch<'0' || ch>'9') { if(ch=='-') f=-1; ch=getchar(); }
    while('0'<=ch && ch<='9') { x=x*10+ch-'0'; ch=getchar(); }
    return x*f;
}
const int MAXN = 500000;
int n, ans, root;
struct Treap {
    int l[MAXN+10], r[MAXN+10], sz[MAXN+10], rnd[MAXN+10], val[MAXN+10], cnt[MAXN+10];
    int ncnt;
    void up(int x) {
        sz[x] = sz[l[x]] + sz[r[x]] + cnt[x];
    }
    void lturn(int &x) {
        int t = r[x]; r[x] = l[t]; l[t] = x; 
        sz[t] = sz[x]; up(x); x= t;
    }
    void rturn(int &x) {
        int t =l[x]; l[x] = r[t]; r[t] = x;
        sz[t] = sz[x]; up(x); x = t;
    }
    int NewNode(int key) {
        ncnt++;
        sz[ncnt] = cnt[ncnt] = 1;
        val[ncnt] = key; rnd[ncnt] = rand();
        return ncnt;
    }
    void ins(int &x, int key) {
        if(!x) {
            x = NewNode(key);
            return ;
        }
        sz[x]++;
        if(val[x] == key) cnt[x]++;
        else if(key > val[x]) {
            ins(r[x], key);
            if(rnd[r[x]] < rnd[x]) lturn(x);
        }
        else {
            ins(l[x], key);
            if(rnd[l[x]] < rnd[x]) rturn(x);
        }
    }
    void del(int &x, int key) {
        if(!x) return ;
        if(val[x] == key) {
            if(cnt[x] > 1) { cnt[x]--; sz[x]--; return ;}
            if(l[x]*r[x] == 0) x = l[x]+r[x];
            else if(rnd[l[x]] < rnd[r[x]]) rturn(x), del(x, key);
            else lturn(x), del(x, key);
        }
        else if(key > val[x]) 
            sz[x]--, del(r[x], key);
        else
            sz[x]--, del(l[x], key);
    }
    int Find_rank(int x, int key) {
        if(!x) return 0;
        if(val[x] == key) return sz[l[x]]+1;
        else if(key > val[x])
            return sz[l[x]]+cnt[x]+Find_rank(r[x], key);
        else return Find_rank(l[x], key);
    }
    int Find_val(int x, int k) {
        if(!x) return 0;
        if(k <= sz[l[x]]) return Find_val(l[x], k);
        else if(k > sz[l[x]]+cnt[x]) 
            return Find_val(r[x], k-sz[l[x]]-cnt[x]);
        return val[x];
    }
    void Find_pre(int x, int key) {
        if(!x) return ;
        if(val[x] < key) {
            ans = x; Find_pre(r[x], key);
        }
        else Find_pre(l[x], key);
    }
    void Find_nex(int x, int key) {
        if(!x) return ;
        if(val[x] > key) {
            ans = x; Find_nex(l[x], key);
        }
        else Find_nex(r[x], key);
    }
} tp;
int main() {
    for (n = read(); n; --n) {
        int op = read(), x = read();
        switch (op) {
            case 1: tp.ins(root, x); break;
            case 2: tp.del(root, x); break;
            case 3: printf("%d\n", tp.Find_rank(root, x)); break;
            case 4: printf("%d\n", tp.Find_val(root, x)); break;
            case 5: ans = 0; tp.Find_pre(root, x); PF("%d\n", tp.val[ans]); break;
            case 6: ans = 0; tp.Find_nex(root, x); PF("%d\n", tp.val[ans]); break;
        }
    }
    return 0;
}