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

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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<stdio.h>
#include<stdlib.h>
 
// A linked list node
struct Node
{
    int data;
    struct Node *next;
};
 
/* We are using a double pointer head_ref
   here because we change head of the
   linked list inside this function.*/
void moveToFront(struct 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 */
    struct Node *secLast = NULL;
    struct 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(struct Node** head_ref,
          int new_data)
{
    // Allocate node
    struct Node* new_node =
           (struct Node*) malloc(sizeof(struct Node));
 
    // Put in the data 
    new_node->data  = new_data;
 
    // Link the old list of 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(struct Node *node)
{
    while(node != NULL)
    {
        printf("%d ", node->data);
        node = node->next;
    }
}
 
// Driver code
int main()
{
    struct 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);
 
    printf("Linked list before moving last to front");
    printList(start);
 
    moveToFront(&start);
 
    printf("Linked list after removing last to front");
    printList(start);
 
    return 0;
}


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) as it is using constant space

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



Last Updated : 14 Mar, 2023
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