15A/B

#include<iostream>
using namespace std;

struct tree
{
    int D;
    tree* l;
    tree* r;
};

void add(tree*& top, int element)
{
    if (top == NULL)
    {
        top = new tree();
        top->D = element;
        top->l = NULL;
        top->r = NULL;
    }
    else if (element < top->D) add(top->l, element);
    else add(top->r, element);
}

void print_pramoi(tree* top)
{
    if (top != NULL)
    {
        cout << "  " << top->D;
        print_pramoi(top->l);
        print_pramoi(top->r);
    }
}

void print_simetr(tree* top)
{
    if (top != NULL)
    {
        print_simetr(top->l);
        cout << "  " << top->D;
        print_simetr(top->r);
    }
}


void print_obr(tree* top)
{
    if (top != NULL)
    {
        print_obr(top->l);
        print_obr(top->r);
        cout << "  " << top->D;
    }
}

void delet(tree* top)
{
    if (top != NULL)
    {
        delet(top->l);
        delet(top->r);
        delete top;
        top = NULL;
    }
}

void part_A(tree* top,int &kolvo)
{
    if (top != NULL  )
    {
        part_A(top->l,kolvo);
        if (top->l != NULL && top->r == NULL)
            if (top->l->l == NULL && top->l->r == NULL)
                kolvo++;
        part_A(top->r,kolvo);
    }
}

tree *found_before_max_in_Right_tree(tree*top)
{
    while (top->r->r != NULL)
        top = top->r;

    return top;
}

void part_B_change_elements(tree*&top_main)
{
    if(top_main->r==NULL){
        cout<<"Right podderevo is empty! Replace is unreal";
        exit(1);
    }

    if(top_main==NULL){
        cout<<"Tree is empty!";
        exit(1);
    }

    if(top_main->r->r==NULL)
    {
        tree* max=top_main->r;
        tree* max_l=max->l;

        tree* top=top_main;
        tree* top_l=top_main->l;

        top_main=max;
        max->l=top_l;
        max->r=top;
        top->l=max_l;
        top->r=NULL;
        return;
    }

    tree* top=top_main;
    tree* before_max=found_before_max_in_Right_tree(top);
    tree* max=before_max->r;

    tree* top_l=top_main->l;
    tree* top_r=top_main->r;

    tree* max_l=max->l;
    tree* max_r=max->r;

    top=top_main;
    top_main=max;
    max->l=top_l;
    max->r=top_r;

    before_max->r=top;
    top->r=max_r;
    top->l=max_l;


}

int main()
{
    tree* top = NULL;
    cout << "Write number of elements: "; int n; cin >> n;
    int element;

    for (int i = 0; i < n; i++)
    {
        cin >> element;
        add(top, element);
    }

    print_simetr(top); cout << endl;
    cout << "Part A: ";
    int kolvo;
    part_A(top,kolvo); cout << kolvo << endl;

    part_B_change_elements(top);

    print_simetr(top);

    cout << endl;

    delet(top);
}