Given a singly linked list and a position, delete a linked list node at the 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 << "
Linked List after Deletion at position 4: "; printList(head);
return 0;
} // This code is contributed by premsai2030 |
Output:
Created Linked List: 8 2 3 1 7 Linked List after Deletion at position 4: 8 2 3 1
Time Complexity: O(n), where n represents the length of the given linked list.
Auxiliary Space: O(1), no extra space is required, so it is a constant.
Please refer complete article on Delete a Linked List node at a given position for more details!