普通平衡树

题目描述

思路

Treap 模板题

代码

#include <cstdio>
#include <cstdlib>
#include <ctime>

const int MAX = 110000 + 5;
int n,m,rt,tot,inf = 0x7f3f3f3f,ot;
char str[100];
struct Node {
    int lc,rc,key,size,cnt,pri;
    #define lc(x) t[x].lc
    #define rc(x) t[x].rc
    #define pri(x) t[x].pri
    #define key(x) t[x].key
    #define size(x) t[x].size
    #define cnt(x) t[x].cnt
} t[MAX];
inline void write(int x) {
    if (x == 0) { putchar('0'); return; }
    if (x < 0) putchar('-'),x = -x;
    ot = 0;
    while (x) str[++ot] = x % 10 + '0',x /= 10;
    while (ot) putchar(str[ot--]);
}
inline int read() {
    int s = 0,f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if (ch == '-') f = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') s = s * 10 + ch - '0',ch = getchar();
    return s * f;
}
void show(int x) {
    printf("%d %d %d %d %d %dn",lc(x),rc(x),pri(x),key(x),size(x),cnt(x));
    if (lc(x)) show(lc(x));
    if (rc(x)) show(rc(x));
}
void pushup(int r) { 
    size(r) = size(lc(r)) + size(rc(r)) + cnt(r); 
}
void zig(int &r) {
    int s = lc(r);
    lc(r) = rc(s);
    rc(s) = r;
    size(s) = size(r);
    pushup(r);
    r = s;
}
void zag(int &r) {
    int s = rc(r);
    rc(r) = lc(s);
    lc(s) = r;
    size(s) = size(r);
    pushup(r);
    r = s;
}
void insert(int &r,int k) {
    if (!r) {
        r = ++tot; pri(r) = rand(); key(r) = k;
        lc(r) = rc(r) = 0;
        size(r) = cnt(r) = 1;
        return;
    } else ++size(r);
    if (key(r) == k) ++cnt(r);
    else if (k < key(r)) {
        insert(lc(r),k);
        if (pri(lc(r)) < pri(r)) zig(r);
    } else {
        insert(rc(r),k);
        if (pri(rc(r)) < pri(r)) zag(r);
    }
}

void del(int &r,int k) {
    if (key(r) == k) {
        if (cnt(r) >= 2) --cnt(r),--size(r);
        else if (!lc(r) || !rc(r)) r = lc(r) + rc(r);
        else if (pri(lc(r)) < pri(rc(r))) {
            zig(r),del(r,k);
        } else {
            zag(r),k);
        }
        return;
    }
    --size(r);
    if (k < key(r)) del(lc(r),k);
    else del(rc(r),k);
}

int queryPre(int k) {
    int r = rt,res = inf;
    while (r) {
        if (k > key(r)) res = key(r),r = rc(r);
        else r = lc(r);
    }
    return res;
}

int queryNxt(int k) {
    int r = rt,res = inf;
    while (r) {
        if (k < key(r)) res = key(r),r = lc(r);
        else r = rc(r);
    }
    return res;
}
int queryKth(int k) {
    int r = rt,res = inf;
    while (r) {
        if (size(lc(r)) < k && size(lc(r)) + cnt(r) >= k) return key(r);
        else if (size(lc(r)) >= k) r = lc(r);
        else k -= size(lc(r)) + cnt(r),r = rc(r);
    }
    return res;
}
int queryRand(int k) {
    int r = rt,res = 0;
    while (r) {
        if (k == key(r)) return res + size(lc(r)) + 1;
        else if (k < key(r)) r = lc(r);
        else res += size(lc(r)) + cnt(r),r = rc(r);
    }
    return res;
}

int main() {
    srand(time(NULL));
    n = read();
    for (int i = 1,p,q; i <= n; ++i) {
        p = read(),q = read();
        // printf("%d %dn",q);
        switch(p) {
            case 1: insert(rt,q); break;
            case 2: del(rt,q); break;
            case 3: m = queryRand(q); write(m); puts(""); break;
            case 4: m = queryKth(q); write(m); puts(""); break;
            case 5: m = queryPre(q); write(m); puts(""); break;
            case 6: m = queryNxt(q); write(m); puts("");
        }
        // show(rt);
    }
    return 0;
}