Randomize tree

#include <iostream>
#include <vector>
#include <math.h>
#include <string>
#include <algorithm>
#include <ctime>

using namespace std;


struct node
{
    int key;
    int size;
    node* left;
    node* right;
    node(int k) { key = k; left = right = 0; size = 1; }
    node() {key = -1; left = right = 0; size = 0; }
};

int getsize(node* p)
{
    if(!p) return 0;
    return p->size;
}


void split (node *t, int k, node* l, node* r) {
    if (getsize(t) == 0) {
        l = new node();
        r = new node();
    }
    else
        if (k < t->key) {
            r = t;
            split (t->left, k, l, r->left);
        }
        else {
            l = t;
            split (t->right, k, l->right, r);
        }
}


node* ffind(node* p, int k)
{
    if( !p ) return 0;
    if( k == p->key )
        return p;
    if( k < p->key )
        return ffind(p->left,k);
    else
        return ffind(p->right,k);
}

bool check(node* p, int k) {
    if (ffind(p, k) == p)
        return true;
    return false;
}

node* insert_at_root (node* t, int k) {
    node* l = new node();
    node* r = new node();
    split(t, k, l, r);
    t = new node(k);
    t->key = k;
    t->left = l;
    t->left = r;
    return t;
}

node* insert (node* t, int k) {
    int r = rand() % (t->size + 1);
    if (r == t->size)
        return t = insert_at_root(t, k);
    if (k < t->key)
        t = insert(t->left, k);
    else
        t = insert(t->right, k);
    return t;
}


node* join(node* l, node* r) {
    int m = l->size;
    int n = r->size;
    int total = m + n;
    if (total == 0) {
        node* t = new node();
        return t;
    }
    int rr = rand() % (total + 1);
    if (rr == 0) r++;
    if (rr < m) {
        // с вероятностью m / (m + n)
        l->right = join(l->right, r);
        return l;
    }
    if (rr < m) {
        // с вероятностью m / (m + n)
        r->left = join(l, r->left);
        return r;
    }
}

node* remove(node* t, int k) {
    if (getsize(t) == 0) {
        t = new node(k);
        return t;
    }
    if (k < t->key)
        t->left = remove(t->left, k);
    else
        if (k > t->key)
            t->right = remove(t->right, k);
        else {
            node* q = join(t->left, t->right);
            t = q;
        }
        return t;
}






int main() {
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    node* t = new node();
    int begin = 0;
    int end = 100;
    for (int i = begin; i <= end; i++) {
        insert(t, i);
    }
    cout << "Время работы insert от " << begin << " до " << end << ": " << double(clock()) << " миллисекунд" << endl;

    for (int i = begin; i <= end; i++) {
        if (check(t, i))
            cout << 1 << endl;
        else
            cout << 0 << endl;
    }
    cout << endl;
    cout << "Время работы check от " << begin << " до " << end << ": " << double(clock()) << " миллисекунд" << endl;
    cout << check(t, 10000) << endl;


    return 0;
}