Linked List Operations - Traverse, Insert and Delete

//C++ Code
//Display the content of the list
void PrintList() {
  
  //1. create a temp node pointing to head
  Node* temp = head;
  
  //2. if the temp node is not null continue 
  //   displaying the content and move to the 
  //   next node till the temp becomes null
  if(temp != NULL) {
    cout<<"\nThe list contains: ";
    while(temp != NULL) {
      cout<<temp->data<<" ";
      temp = temp->next;
    }
  } else {
    
    //3. If the temp node is null at the start, 
    //   the list is empty
    cout<<"\nThe list is empty.";
  }
} 

//C++ Code
//Inserts a new node at the start 
void push_front(int newElement) {
  
  //1. allocate a new node
  Node* newNode = new Node();
  
  //2. assign data element 
  newNode->data = newElement;
  
  //3. make next node of new node as head
  newNode->next = head;
  
  //4. make new node as head 
  head = newNode;   
}

//C++ Code
//Inserts a new node at the given position
void push_at(int newElement, int position) {
  
  //1. allocate node to new element
  Node* newNode = new Node(); 
  newNode->data = newElement;
  newNode->next = NULL;

  //2. check if the position is > 0
  if(position < 1) {
    cout<<"\nposition should be >= 1.";
  } else if (position == 1) {
  
  //3. if the position is 1, make next of the
  //   new node as head and new node as head
    newNode->next = head;
    head = newNode;
  } else {

   //4. Else, make a temp node and traverse to the 
   //   node previous to the position
    Node* temp = head;
    for(int i = 1; i < position-1; i++) {
      if(temp != NULL) {
        temp = temp->next;
      }
    }
 
    //5. If the previous node is not null, make 
    //   newNode next as temp next and temp next 
    //   as newNode.
    if(temp != NULL) {
      newNode->next = temp->next;
      temp->next = newNode;  
    } else {
      
      //6. When the previous node is null
      cout<<"\nThe previous node is null.";
    } 
  }
}

//C++ Code
//Inserts a new node at the end
void push_back(int newElement) {
  
  //1. allocate node
  Node* newNode = new Node();
  
  //2. assign data element
  newNode->data = newElement;
  
  //3. assign null to the next of new node
  newNode->next = NULL; 
  
  //4. Check the list is empty or not,
  //   if empty make the new node as head 
  if(head == NULL) {
    head = newNode;
  } else {
    
    //5. Else, traverse to the last node
    Node* temp = head;
    while(temp->next != NULL)
      temp = temp->next;
    
    //6. Change the next of last node to new node
    temp->next = newNode;
  }    
}

//C++ Code
//Deletes the first node
void pop_front() {
  if(head != NULL) {
    
    //1. if head is not null, create a
    //   temp node pointing to head
    Node* temp = head;

    //2. move head to next of head
    head = head->next; 

    //3. delete temp node
    free(temp); 
  }
}

//C++ Code
//Deletes the node at given position
void pop_at(int position) {     
  
  //1. check if the position is > 0
  if(position < 1) {
    cout<<"\nposition should be >= 1.";
  } else if (position == 1 && head != NULL) {
      
    //2. if the position is 1 and head is not null,
    //   make head to head next and delete the 
    //   previous head
    Node* nodeToDelete = head;
    head = head->next;
    free(nodeToDelete);
  } else {
    
    //3. Else, make a temp node and traverse to the 
    //   node previous to the position
    Node* temp = head;
    for(int i = 1; i < position-1; i++) {
      if(temp != NULL) {
        temp = temp->next;
      }
    }
 
    //4. If the previous node and next of the previous  
    //   is not null, adjust links 
    if(temp != NULL && temp->next != NULL) {
        Node* nodeToDelete = temp->next;
        temp->next = temp->next->next;
        free(nodeToDelete); 
    } else {

      //5. Else the given node will be empty.
      cout<<"\nThe node is already null.";
    }       
  }
} 

//C++ Code
//Deletes the last node
void pop_back() {
  if(head != NULL) {
    
    //1. if head in not null and next of head
    //   is null, release the head
    if(head->next == NULL) {
      head = NULL;
    } else {
      
      //2. Else, traverse to the second last 
      //   element of the list
      Node* temp = head;
      while(temp->next->next != NULL)
        temp = temp->next;
      
      //3. Change the next of the second 
      //   last node to null and delete the
      //   last node
      Node* lastNode = temp->next;
      temp->next = NULL; 
      free(lastNode);
    }
  }
}