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

  • Last Updated : 14 Dec, 2021

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.

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


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