Java Program For Recursive Selection Sort For Singly Linked List - Swapping Node Links

// Java implementation of recursive 
// selection sort for singly linked 
// list | Swapping node links 
class GFG{
    
// A Linked list node 
static class Node
{ 
    int data; 
    Node next; 
}; 

// Function to swap nodes 'currX' 
// and 'currY' in a linked list 
// without swapping data 
static Node swapNodes(Node head_ref, 
                      Node currX, 
                      Node currY, 
                      Node prevY) 
{ 
    // Make 'currY' as new head 
    head_ref = currY; 

    // Adjust links 
    prevY.next = currX; 

    // Swap next pointers 
    Node temp = currY.next; 
    currY.next = currX.next; 
    currX.next = temp; 
    return head_ref;
} 

// function to sort the linked list using 
// recursive selection sort technique 
static Node recurSelectionSort(Node head) 
{ 
    // If there is only a single node 
    if (head.next == null) 
        return head; 

    // 'min' - pointer to store the node 
    // having minimum data value 
    Node min = head; 

    // 'beforeMin' - pointer to store 
    // node previous to 'min' node 
    Node beforeMin = null; 
    Node ptr; 

    // Traverse the list till the 
    // last node 
    for (ptr = head; ptr.next != null; 
         ptr = ptr.next) 
    { 
        // If true, then update 'min' and 
        // 'beforeMin' 
        if (ptr.next.data < min.data) 
        { 
            min = ptr.next; 
            beforeMin = ptr; 
        } 
    } 

    // If 'min' and 'head' are not same, 
    // swap the head node with the 'min' node 
    if (min != head) 
        head = swapNodes(head, head, 
                         min, beforeMin); 

    // Recursively sort the remaining list 
    head.next = 
         recurSelectionSort(head.next); 

    return head; 
} 

// Function to sort the given linked list 
static Node sort(Node head_ref) 
{ 
    // If list is empty 
    if ((head_ref) == null) 
        return null; 

    // Sort the list using recursive 
    // selection sort technique 
    head_ref = recurSelectionSort(head_ref); 
    return head_ref;
} 

// Function to insert a node at the 
// beginning of the linked list 
static Node 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 to the 
    // new node 
    new_node.next = (head_ref); 

    // Move the head to point to the 
    // new node 
    (head_ref) = new_node; 
    return head_ref;
} 

// Function to print the linked list 
static void printList( Node head) 
{ 
    while (head != null) 
    { 
        System.out.print(head.data + " "); 
        head = head.next; 
    } 
} 

// Driver code 
public static void main(String args[])
{ 
    Node head = null; 

    // Create linked list 10.12.8.4.6 
    head = push(head, 6); 
    head = push(head, 4); 
    head = push(head, 8); 
    head = push(head, 12); 
    head = push(head, 10); 

    System.out.println( 
    "Linked list before sorting:"); 
    printList(head); 

    // sort the linked list 
    head = sort(head); 

    System.out.print( 
    "Linked list after sorting:"); 
    printList(head); 
} 
} 
// This code is contributed by Arnab Kundu