Delete a Linked List node at a given position - Dieptranivsr/DroneIVSR GitHub Wiki

Delete a Linked List node at a given position Example:

Input: position = 1, Linked List = 8->2->3->1->7
Output: Linked List =  8->3->1->7

Input: position = 0, Linked List = 8->2->3->1->7
Output: Linked List = 2->3->1->7

If the node to be deleted is the root, simply delete it. To delete a middle node, we must have a pointer to the node previous to the node to be deleted. So if positions are not zero, we run a loop position-1 times and get a pointer to the previous node.

Below is the implementation of the above idea.

// A complete working C++ program to delete
// a node in a linked list at a given position
#include <iostream>
using namespace std;

// A linked list node
class Node
{
	public:
	int data;
	Node *next;
};

// Given a reference (pointer to pointer) to
// the head of a list and an int inserts a
// new node on the front of the list.
void push(Node** head_ref, int new_data)
{
	Node* new_node = new Node();
	new_node->data = new_data;
	new_node->next = (*head_ref);
	(*head_ref) = new_node;
}

// Given a reference (pointer to pointer) to
// the head of a list and a position, deletes
// the node at the given position
void deleteNode(Node **head_ref, int position)
{
	
	// If linked list is empty
	if (*head_ref == NULL)
		return;
	
	// Store head node
	Node* temp = *head_ref;

	// If head needs to be removed
	if (position == 0)
	{
		
		// Change head
		*head_ref = temp->next;
		
		// Free old head
		free(temp);			
		return;
	}

	// Find previous node of the node to be deleted
	for(int i = 0; temp != NULL && i < position - 1; i++)
		temp = temp->next;

	// If position is more than number of nodes
	if (temp == NULL || temp->next == NULL)
		return;

	// Node temp->next is the node to be deleted
	// Store pointer to the next of node to be deleted
	Node *next = temp->next->next;

	// Unlink the node from linked list
	free(temp->next); // Free memory
	
	// Unlink the deleted node from list
	temp->next = next;
}

// This function prints contents of linked
// list starting from the given node
void printList( Node *node)
{
	while (node != NULL)
	{
		cout << node->data << " ";
		node = node->next;
	}
}

// Driver code
int main()
{
	// Start with the empty list
	Node* head = NULL;

	push(&head, 7);
	push(&head, 1);
	push(&head, 3);
	push(&head, 2);
	push(&head, 8);

	cout << "Created Linked List: ";
	printList(head);
	deleteNode(&head, 4);
	cout << "\nLinked List after Deletion at position 4: ";
	printList(head);
	return 0;
}

Output:

  Created Linked List: 
   8  2  3  1  7 
  Linked List after Deletion at position 4: 
   8  2  3  1
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