C Exercises: Rotate a singly linked list to the right by k places

C Singly Linked List : Exercise-23 with Solution

Write a C program that rotates a singly linked list to the right by k places.

Sample Solution:

C Code:

#include<stdio.h>
#include <stdlib.h>


struct Node {
    int data;
    struct Node* next;
};

// Function to create a new node
struct Node* newNode(int data) {
    struct Node* node = (struct Node*) malloc(sizeof(struct Node));
    node->data = data;
    node->next = NULL;
    return node;
}

// Function to display a linked list
void displayList(struct Node* head) {
    while (head) {
        printf("%d ", head->data);
        head = head->next;
    }
    printf("\n");
}

// Function to rotate a linked list by a given number of positions
void rotate_List(struct Node** head_ref, int k) {
    struct Node* current = *head_ref;
    int count = 1;

    // find the last node of the linked list
    while (current->next) {
        current = current->next;
        count++;
    }

    // set the next of the last node to the head
    current->next = *head_ref;

    // find the (count - k % count)th node from the beginning
    for (int i = 0; i < count - k % count; i++) {
        current = current->next;
    }

    // set the (count - k % count)th node as the new head
    *head_ref = current->next;
    current->next = NULL;
}

int main() {
    struct Node* list1 = newNode(1);
    list1->next = newNode(3);
    list1->next->next = newNode(4);
    list1->next->next->next = newNode(7);   
    list1->next->next->next->next = newNode(9);

    printf("Original List: ");
    displayList(list1);
    int k = 1;
    printf("\nRotate the said singly linked list to the right by %d places:\n", k);
    rotate_List(&list1, k);
    displayList(list1);
    k = 2;
    printf("\nRotate the said singly linked list to the right by %d places:\n", k);
    rotate_List(&list1, k);
    displayList(list1);
    k = 4;
    printf("\nRotate the said singly linked list to the right by %d places:\n", k);
    rotate_List(&list1, k);
    displayList(list1);
    return 0;
}

Sample Output:

Original List: 1 3 4 7 9 

Rotate the said singly linked list to the right by 1 places:
9 1 3 4 7 

Rotate the said singly linked list to the right by 2 places:
4 7 9 1 3 

Rotate the said singly linked list to the right by 4 places:
7 9 1 3 4 

Flowchart :

C Programming Code Editor:

Previous: Add two numbers represented by linked lists.
Next: Change K^th node from beginning to end in a linked list.