Bubble Sort for Linked List by Swapping nodes

Given a singly linked list, sort it using bubble sort by swapping nodes.

Examples:

Input: 10->30->20->5
Output: 5->10->20->30

Input: 20->4->3
Output: 3->4->20

Approach:

1. Get the Linked List to be sorted
2. Apply Bubble Sort to this linked list, in which, while comparing the two adjacent nodes, actual nodes are swapped instead of just swapping the data.
3. Print the sorted list

Below is the implementation of the above approach: 

C++

// C++ program to sort Linked List
// using Bubble Sort
// by swapping nodes

#include <iostream>
using namespace std;

/* structure for a node */
struct Node
{
    int data;
    struct Node* next;
} Node;

/*Function to swap the nodes */
struct Node* swap(struct Node* ptr1, struct Node* ptr2)
{
    struct Node* tmp = ptr2->next;
    ptr2->next = ptr1;
    ptr1->next = tmp;
    return ptr2;
}

/* Function to sort the list */
int bubbleSort(struct Node** head, int count)
{
    struct Node** h;
    int i, j, swapped;

    for (i = 0; i <= count; i++)
    {

        h = head;
        swapped = 0;

        for (j = 0; j < count - i - 1; j++)
        {

            struct Node* p1 = *h;
            struct Node* p2 = p1->next;

            if (p1->data > p2->data)
            {

                /* update the link after swapping */
                *h = swap(p1, p2);
                swapped = 1;
            }

            h = &(*h)->next;
        }

        /* break if the loop ended without any swap */
        if (swapped == 0)
            break;
    }
}

/* Function to print the list */
void printList(struct Node* n)
{
    while (n != NULL)
    {
        cout << n->data << " -> ";
        n = n->next;
    }
    cout << endl;
}

/* Function to insert a struct Node
at the beginning of a linked list */
void insertAtTheBegin(struct Node** start_ref, int data)
{
    struct Node* ptr1
        = (struct Node*)malloc(sizeof(struct Node));

    ptr1->data = data;
    ptr1->next = *start_ref;
    *start_ref = ptr1;
}

// Driver Code
int main()
{
    int arr[] = { 78, 20, 10, 32, 1, 5 };
    int list_size, i;

    /* start with empty linked list */
    struct Node* start = NULL;
    list_size = sizeof(arr) / sizeof(arr[0]);

    /* Create linked list from the array arr[] */
    for (i = 0; i < list_size; i++)
        insertAtTheBegin(&start, arr[i]);

    /* print list before sorting */
    cout <<"Linked list before sorting\n";
    printList(start);

    /* sort the linked list */
    bubbleSort(&start, list_size);

    /* print list after sorting */
    cout <<"Linked list after sorting\n";
    printList(start);

    return 0;
}

// This code is contributed by
// shubhamsingh10

C

// C program to sort Linked List
// using Bubble Sort
// by swapping nodes

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

/* structure for a node */
struct Node {
    int data;
    struct Node* next;
} Node;

/*Function to swap the nodes */
struct Node* swap(struct Node* ptr1, struct Node* ptr2)
{
    struct Node* tmp = ptr2->next;
    ptr2->next = ptr1;
    ptr1->next = tmp;
    return ptr2;
}

/* Function to sort the list */
int bubbleSort(struct Node** head, int count)
{
    struct Node** h;
    int i, j, swapped;

    for (i = 0; i <= count; i++) {

        h = head;
        swapped = 0;

        for (j = 0; j < count - i - 1; j++) {

            struct Node* p1 = *h;
            struct Node* p2 = p1->next;

            if (p1->data > p2->data) {

                /* update the link after swapping */
                *h = swap(p1, p2);
                swapped = 1;
            }

            h = &(*h)->next;
        }

        /* break if the loop ended without any swap */
        if (swapped == 0)
            break;
    }
}

/* Function to print the list */
void printList(struct Node* n)
{
    while (n != NULL) {
        printf("%d -> ", n->data);
        n = n->next;
    }
    printf("\n");
}

/* Function to insert a struct Node
   at the beginning of a linked list */
void insertAtTheBegin(struct Node** start_ref, int data)
{
    struct Node* ptr1
        = (struct Node*)malloc(sizeof(struct Node));

    ptr1->data = data;
    ptr1->next = *start_ref;
    *start_ref = ptr1;
}

// Driver Code
int main()
{
    int arr[] = { 78, 20, 10, 32, 1, 5 };
    int list_size, i;

    /* start with empty linked list */
    struct Node* start = NULL;
    list_size = sizeof(arr) / sizeof(arr[0]);

    /* Create linked list from the array arr[] */
    for (i = 0; i < list_size; i++)
        insertAtTheBegin(&start, arr[i]);

    /* print list before sorting */
    printf("Linked list before sorting\n");
    printList(start);

    /* sort the linked list */
    bubbleSort(&start, list_size);

    /* print list after sorting */
    printf("Linked list after sorting\n");
    printList(start);

    return 0;
}

Output:

Linked list before sorting
5 -> 1 -> 32 -> 10 -> 20 -> 78 -> 
Linked list after sorting
1 -> 5 -> 10 -> 20 -> 32 -> 78 ->

Time complexity: O(N^2), where N is the number of nodes in the Linked List.
Auxiliary space: O(1)