Treap的插入删除实现

详见：随机平衡二叉查找树Treap的分析与应用

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>


#define CL(arr, val)    memset(arr, val, sizeof(arr))
#define REP(i, n)       for(i = 0; i < n; ++i)
#define FOR(i, l, h)    for(i = l; i <= h; ++i)
#define FORD(i, h, l)   for(i = h; i >= l; --i)
#define L(x)    x << 1
#define R(x)    x << 1 | 1
#define MID(l, r)  (l + r) >> 1
typedef long long LL;

using namespace std;

struct Treap_node {
    Treap_node *left, *right;
    int val, fix;
};

void Left_Rotate(Treap_node* & a) {    //左旋转操作
    Treap_node *b = a->right;
    a->right = b->left;
    b->left = a;
    a = b;
}

void Right_Rotote(Treap_node*& a) {    //右旋转操作
    Treap_node * b = a->left;
    a->left = b->right;
    b->right = a;
    a = b;
}

void insert(Treap_node*& p, int val) {    //插入
    if(!p) {
        p = new Treap_node;
        p->val = val;
        p->fix = rand();
    } else if(val <= p->val) {
        insert(p->left, val);
        if(p->left->fix < p->fix)
            Right_Rotote(p);
    } else {
        insert(p->right, val);
        if(p->right->fix < p->fix)
            Left_Rotate(p);
    }
}


void del(Treap_node*& p, int val) {    //删除
    if(val == p->val) {
        if(!p->left || !p->right) {
            Treap_node* t = p;
            if(!p->right)   p = p->left;
            else    p = p->right;
            delete t;
        } else {
            if(p->left->fix < p->right->fix) {
                Right_Rotote(p);
                del(p->right, val);
            }
            else {
                Left_Rotate(p);
                del(p->left, val);
            }
        }
    } else if(val < p->val) del(p->left, val);
    else    del(p->right, val);
}

void display(Treap_node*& p) {    //可以看到建好的Treap结构
    if(p != NULL) {
        if(p->left != NULL && p->right == NULL)     printf("%d %d : l%d\n", p->val, p->fix, p->left->val);
        else if(p->left == NULL && p->right == NULL)    printf("%d %d\n", p->val, p->fix);
        else if(p->left == NULL && p->right != NULL)    printf("%d %d : r%d\n", p->val, p->fix, p->right->val);
        else    printf("%d %d : l%d r%d\n", p->val, p->fix, p->left->val, p->right->val);
        display(p->left);
        display(p->right);
    }
}

int main() {
    Treap_node* root;
    int i;
    root = NULL;
    REP(i, 10)  insert(root, i);
    display(root);
}