C++ Program To Delete Alternate Nodes Of A Linked List
Given a Singly Linked List, starting from the second node delete all alternate nodes of it. For example, if the given linked list is 1->2->3->4->5 then your function should convert it to 1->3->5, and if the given linked list is 1->2->3->4 then convert it to 1->3.
Method 1 (Iterative):
Keep track of previous of the node to be deleted. First, change the next link of the previous node and iteratively move to the next node.
C++
#include <bits/stdc++.h>
using namespace std;
class Node
{
public :
int data;
Node *next;
};
void deleteAlt(Node *head)
{
if (head == NULL)
return ;
Node *prev = head;
Node *node = head->next;
while (prev != NULL &&
node != NULL)
{
prev->next = node->next;
prev = prev->next;
if (prev != NULL)
node = prev->next;
}
}
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;
}
void printList(Node *node)
{
while (node != NULL)
{
cout << node->data << " " ;
node = node->next;
}
}
int main()
{
Node* head = NULL;
push(&head, 5);
push(&head, 4);
push(&head, 3);
push(&head, 2);
push(&head, 1);
cout << "List before calling deleteAlt() " ;
printList(head);
deleteAlt(head);
cout << "List after calling deleteAlt() " ;
printList(head);
return 0;
}
|
Output:
List before calling deleteAlt()
1 2 3 4 5
List after calling deleteAlt()
1 3 5
Time Complexity: O(n) where n is the number of nodes in the given Linked List.
Auxiliary Space: O(1) because it is using constant space
Method 2 (Recursive):
Recursive code uses the same approach as method 1. The recursive code is simple and short but causes O(n) recursive function calls for a linked list of size n.
C++
void deleteAlt(Node *head)
{
if (head == NULL)
return ;
Node *node = head->next;
if (node == NULL)
return ;
head->next = node->next;
free (node);
deleteAlt(head->next);
}
|
Time Complexity: O(n)
Auxiliary space: O(n) for call stack because using recursion
Please refer complete article on Delete alternate nodes of a Linked List for more details!
Last Updated :
10 Jan, 2023
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