C++ Dynamic Memory Allocation: Linked list operations with memory allocation

Last update on December 20 2024 12:29:05 (UTC/GMT +8 hours)

Write a C++ program to dynamically allocate memory for a linked list and perform basic operations like insert and delete node(s).

Sample Solution:

C Code:

#include <iostream> // Including the Input/Output Stream Library

// Definition of a structure named Node for a linked list
struct Node {
  int data; // Data stored in the node
  Node * next; // Pointer to the next node
};

// Function to display the linked list
void displayList(Node * head) {
  Node * current = head; // Initialize a pointer 'current' to traverse the list
  while (current != nullptr) { // Loop through the list until the end
    std::cout << current->data << " "; // Output the data in the current node
    current = current->next; // Move to the next node
  }
  std::cout << std::endl; // Output a new line after printing the list
}

// Function to insert a node at the beginning of the linked list
void insertAtBeginning(Node * & head, int value) {
  Node * newNode = new Node; // Create a new node
  newNode->data = value; // Set the data of the new node
  newNode->next = head; // Point the new node to the current head
  head = newNode; // Update the head to the new node
}

// Function to delete a node from the linked list
void deleteNode(Node * & head, int value) {
  if (head == nullptr) {
    return; // Empty list, nothing to delete
  }
  if (head->data == value) {
    Node * temp = head; // Store the current head in a temporary node
    head = head->next; // Move the head to the next node
    delete temp; // Delete the original head node
    return;
  }
  Node * current = head; // Initialize a pointer 'current' to traverse the list
  while (current->next != nullptr) { // Traverse until the end of the list
    if (current->next->data == value) { // Check if the next node has the value to be deleted
      Node * temp = current->next; // Store the next node in a temporary node
      current->next = temp->next; // Update the pointers to skip the node to be deleted
      delete temp; // Delete the node with the value
      return;
    }
    current = current->next; // Move to the next node
  }
}

// Function to deallocate the memory of the linked list
void deleteList(Node * & head) {
  Node * current = head; // Initialize a pointer 'current' to traverse the list
  while (current != nullptr) { // Loop until the end of the list
    Node * temp = current; // Store the current node in a temporary node
    current = current->next; // Move to the next node
    delete temp; // Delete the stored node
  }
  head = nullptr; // Set the head to null after deleting all nodes
}

int main() {
  Node * head = nullptr; // Initialize an empty linked list

  // Insert nodes at the beginning
  insertAtBeginning(head, 1);
  insertAtBeginning(head, 3);
  insertAtBeginning(head, 5);
  insertAtBeginning(head, 7);
  insertAtBeginning(head, 9);

  // Display the initial linked list
  std::cout << "Initial list: ";
  displayList(head);

  // Delete a node from the linked list
  std::cout << "Remove the Node 3: ";
  deleteNode(head, 3);
  // Display the updated linked list
  std::cout << "\nUpdated list: ";
  displayList(head);

  // Deallocate the memory of the linked list
  deleteList(head);

  return 0; // Returning 0 to indicate successful execution of the program
}

Sample Output:

Initial list: 9 7 5 3 1
Remove the Node 3:
Updated list: 9 7 5 1

Explanation:

In the above exercise, we define a Node structure to represent each node of the linked list. Each node contains a data field and a pointer to the next node.

There are several functions to perform basic operations on the linked list:

• displayList() function displays the elements of the linked list.
• insertAtBeginning() function inserts a new node at the beginning of the linked list.
• deleteNode() function deletes a node with a specified value from the linked list.
• deleteList() function deallocates the memory of the entire linked list.

Inside the main() function, we first initialize an empty linked list by setting the head to nullptr.

• Next we insert nodes at the beginning of the linked list using insertAtBeginning() and delete a specific node using deleteNode() function.
• After each operation, we display the linked list using displayList().
• Finally, deallocate the linked list memory using deleteList() to free the memory occupied by the linked list.

Flowchart:

CPP Code Editor:

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