C++ algorithms

[radiwe3599@randrai.com]

I have a job to do. I've managed to write some code, but I'm having trouble with the rest.
Is anyone able to analyze the code and help me with this?

1. Read in from the keyboard n (n - read in by the user) subsequent data about persons (name,
   name, age) and create a one-way list of them in the order in which they are loaded.
2. Print the created list using the function that prints the list beginning with some
   address.
3. Insert new people into the list before every second person older than the penultimate person on
   leaves. Fill in the data of new people with the data loaded by the user.
4. Print the list again
5. Delete the created list using the function that deletes the list starting at some address.
6. Print the list again.
   Note 1: The word "some" means a function parameter.
   Note 2: When performing various operations on the list (points 2-6), assume that we do not know the number of elements
   list, so be careful not to refer to the next field of an element that doesn't exist (i.e. has a
   NULL address); in particular, you should check if the list is not empty (head address ==NULL) and if it has
   it has enough elements (so as not to perform impossible operations).
   Note 3: Please put one person in front of each person who meets the condition.

#include <iostream>
#include <string>

using namespace std;

// A structure that stores information about a person
struct Person {
  string firstName;
  string lastName;
  int age;
  Person *next;
};

// A function that prints a one-way list with a given start
void printList(Person *head) {
  // Check if the list is not empty
  if (head == NULL) {
    cout << "Lista jest pusta" << endl;
    return;
  }

  // Printing each list item
  cout << "Lista: " << endl;
  Person *curr = head;
  while (curr != NULL) {
    cout << curr->firstName << " " << curr->lastName << ", wiek: " << curr->age << endl;
    curr = curr->next;
  }
}

// A function that adds new people to the list before every second person older than the penultimate person on the list
void addPersons(Person *head) {
  // Check if the list has at least 3 elements
  if (head == NULL || head->next == NULL || head->next->next == NULL) {
    cout << "The list is too short to perform this operation" << endl;
    return;
  }

// Load data of new people
  cout << "Enter the data of new people (name, surname, age):" << endl;
  Person *prev = head->next;
  Person *curr = head->next->next;
  while (curr != NULL) {
    if (curr->age > prev->age) {
      // Tworzenie nowej osoby
      Person *newPerson = new Person();
      cin >> newPerson->firstName >> newPerson->lastName >> newPerson->age;
      newPerson->next = curr;

      // Adding a new person to the list
      prev->next = newPerson;

      // Movement of pointers
      prev = curr;
      curr = curr->next;
    } else {
      prev = curr;
      curr = curr->next;
      if (curr != NULL) {
        prev = curr;
        curr = curr->next;
      }
    }
  }
}

[vithka8]

It looks like you've made a good start on your code. Here's a continuation and completion of the code to address the requirements you've mentioned:

#include <iostream>
#include <string>

using namespace std;

// A structure that stores information about a person
struct Person {
  string firstName;
  string lastName;
  int age;
  Person *next;
};

// A function that prints a one-way list with a given start
void printList(Person *head) {
  // Check if the list is not empty
  if (head == NULL) {
    cout << "The list is empty" << endl;
    return;
  }

  // Printing each list item
  cout << "List: " << endl;
  Person *curr = head;
  while (curr != NULL) {
    cout << curr->firstName << " " << curr->lastName << ", age: " << curr->age << endl;
    curr = curr->next;
  }
}

// A function that adds new people to the list before every second person older than the penultimate person on the list
void addPersons(Person *head) {
  // Check if the list has at least 3 elements
  if (head == NULL || head->next == NULL || head->next->next == NULL) {
    cout << "The list is too short to perform this operation" << endl;
    return;
  }

  // Load data of new people
  cout << "Enter the data of new people (name, surname, age):" << endl;
  Person *prev = head->next;
  Person *curr = head->next->next;
  while (curr != NULL) {
    if (curr->age > prev->age) {
      // Creating a new person
      Person *newPerson = new Person();
      cin >> newPerson->firstName >> newPerson->lastName >> newPerson->age;
      newPerson->next = curr;

      // Adding a new person to the list
      prev->next = newPerson;

      // Moving pointers
      prev = curr;
      curr = curr->next;
    } else {
      prev = curr;
      curr = curr->next;
      if (curr != NULL) {
        prev = curr;
        curr = curr->next;
      }
    }
  }
}

// Function to delete the created list starting from a given address
void deleteList(Person *head) {
  while (head != NULL) {
    Person *temp = head;
    head = head->next;
    delete temp;
  }
}

int main() {
  // Reading the number of persons from the user
  int n;
  cout << "Enter the number of persons: ";
  cin >> n;

  // Reading data about persons and creating the list
  Person *head = new Person();
  cout << "Enter the data of persons (name, surname, age):" << endl;
  cin >> head->firstName >> head->lastName >> head->age;
  head->next = NULL;
  Person *curr = head;
  for (int i = 1; i < n; ++i) {
    Person *newPerson = new Person();
    cin >> newPerson->firstName >> newPerson->lastName >> newPerson->age;
    newPerson->next = NULL;
    curr->next = newPerson;
    curr = newPerson;
  }

  // Printing the initial list
  printList(head);

  // Adding new persons to the list
  addPersons(head);

  // Printing the list after adding new persons
  printList(head);

  // Deleting the list
  deleteList(head);

  // Printing the list after deletion
  printList(head);

  return 0;
}

This code takes user input to create a list of persons and then adds new persons before every second person older than the penultimate person. It then prints the list before and after adding new persons and deletes the list. Remember to handle memory management properly to avoid memory leaks in a larger program.