списки

#include <iostream>
using namespace std;

class node {
public:
    int data;
    node* next;

    node(int value)
    {
        data = value;
        next = NULL;
    }
};

void insertathead(node*& head, int val)
{
    node* n = new node(val);
    n->next = head;
    head = n;
}

void insertafter(node* head, int key, int val)
{
    node* n = new node(val);
    if (key == head->data) {
        n->next = head->next;
        head->next = n;
        return;
    }

    node* temp = head;
    while (temp->data != key) {
        temp = temp->next;
        if (temp == NULL) {
            return;
        }
    }
    n->next = temp->next;
    temp->next = n;
}

void insertattail(node*& head, int val)
{
    node* n = new node(val);
    if (head == NULL) {
        head = n;
        return;
    }

    node* temp = head;
    while (temp->next != NULL) {
        temp = temp->next;
    }
    temp->next = n;
}

void print(node*& head)
{
    node* temp = head;

    while (temp != NULL) {
        cout << temp->data << " ";
        temp = temp->next;
    }
}

int main()
{
    setlocale(0, "");
    node* head = NULL;
    int size = 30;
    int* arr = new int[size];
    for (int i = 0; i < size; i++)
        arr[i] = rand() % 20;

    for (int i = 0; i < size; i++)
        insertathead(head, arr[i]);
    print(head);

    int key, val;
    cout << "\nВкажiть ключ: ";
    cin >> key;
    cout << "\nВкажiть елемент: ";
    cin >> val;

    insertafter(head, key, val);
    cout << "\nПiсля вставки нового елемента: " << endl;
    print(head);
    cout << endl;

    return 0;
}