Open In App

C++ Program For Moving Last Element To Front Of A Given Linked List

Improve
Improve
Like Article
Like
Save
Share
Report

Write a function that moves the last element to the front in a given Singly Linked List. For example, if the given Linked List is 1->2->3->4->5, then the function should change the list to 5->1->2->3->4. Algorithm: Traverse the list till the last node. Use two pointers: one to store the address of the last node and the other for the address of the second last node. After the end of the loop do the following operations.

  1. Make second last as last (secLast->next = NULL).
  2. Set next of last as head (last->next = *head_ref).
  3. Make last as head ( *head_ref = last).

C++




/* C++ Program to move last element
   to front in a given linked list */
#include <bits/stdc++.h>
using namespace std;
 
// A linked list node
class Node
{
    public:
    int data;
    Node *next;
};
 
/* We are using a double pointer
   head_ref here because we change
   head of the linked list inside
   this function.*/
void moveToFront(Node **head_ref)
{
    /* If linked list is empty, or
       it contains only one node,
       then nothing needs to be done,
       simply return */
    if (*head_ref == NULL ||
       (*head_ref)->next == NULL)
        return;
 
    /* Initialize second last
       and last pointers */
    Node *secLast = NULL;
    Node *last = *head_ref;
 
    /* After this loop secLast contains
       address of second last node and
       last contains address of last node
       in Linked List */
    while (last->next != NULL)
    {
        secLast = last;
        last = last->next;
    }
 
    // Set the next of second last as NULL
    secLast->next = NULL;
 
    // Set next of last as head node
    last->next = *head_ref;
 
    /* Change the head pointer
       to point to last node now */
    *head_ref = last;
}
 
// UTILITY FUNCTIONS
/* Function to add a node
   at the beginning of Linked List */
void push(Node** head_ref,
          int new_data)
{
    // Allocate node
    Node* new_node = new Node();
 
    // Put in the data
    new_node->data = new_data;
 
    // Link the old list off the
    // new node
    new_node->next = (*head_ref);
 
    // Move the head to point to the
    // new node
    (*head_ref) = new_node;
}
 
/* Function to print nodes in a
   given linked list */
void printList(Node *node)
{
    while(node != NULL)
    {
        cout << node->data << " ";
        node = node->next;
    }
}
 
// Driver code
int main()
{
    Node *start = NULL;
 
    /* The constructed linked list is:
       1->2->3->4->5 */
    push(&start, 5);
    push(&start, 4);
    push(&start, 3);
    push(&start, 2);
    push(&start, 1);
 
    cout <<
    "Linked list before moving last to front";
    printList(start);
 
    moveToFront(&start);
 
    cout <<
    "Linked list after removing last to front";
    printList(start);
 
    return 0;
}
// This code is contributed by rathbhupendra


Output:

Linked list before moving last to front 
1 2 3 4 5 
Linked list after removing last to front 
5 1 2 3 4

Time Complexity: O(n) where n is the number of nodes in the given Linked List.

Auxiliary Space: O(1) because using constant variables

Please refer complete article on Move last element to front of a given Linked List for more details!



Last Updated : 03 Aug, 2022
Like Article
Save Article
Previous
Next
Share your thoughts in the comments
Similar Reads