Iterative selection sort for linked list
Given a linked list, the task is to sort the linked list in ascending order by using selection sort.
Examples:
Input : 1->4->2->2->3 Output : 1->2->2->3->4 Input : 5->4->3->2 Output : 2->3->4->5
Selection Sort Algorithm: Iterate the given list N times where N is the number of elements in the list. In every iteration of selection sort, the minimum element (considering ascending order) from the unsorted subarray is picked and moved to the sorted subarray.
Example:
list = 64 25 12 22 11 // Find the minimum element in list(0...4) // and place it at beginning 11 25 12 22 64 // Find the minimum element in list(1...4) // and place it at beginning of list(1...4) 11 12 25 22 64 // Find the minimum element in list(2...4) // and place it at beginning of list(2...4) 11 12 22 25 64 // Find the minimum element in list(3...4) // and place it at beginning of list(3...4) 11 12 22 25 64
The swapping required can be done in two ways:
- By swapping the data parts of the nodes.
- By swapping the complete nodes.
Second implementation is generally used when elements of the list are some kind of records because in such a case data swapping becomes tedious and expensive due to the presence of a large number of data elements.
Implementation Method 1: Below is the implementation of selection sort function for sorting linked lists by swapping only data parts of a node.
C++
void selectionSort(node* head) { node* temp = head; // Traverse the List while (temp) { node* min = temp; node* r = temp->next; // Traverse the unsorted sublist while (r) { if (min->data > r->data) min = r; r = r->next; } // Swap Data int x = temp->data; temp->data = min->data; min->data = x; temp = temp->next; } } |
Java
void selectionSort(node head) { node temp = head; // Traverse the List while (temp) { node min = temp; node r = temp.next; // Traverse the unsorted sublist while (r) { if (min.data > r.data) min = r; r = r.next; } // Swap Data int x = temp.data; temp.data = min.data; min.data = x; temp = temp.next; } } // This code is contributed by shivanisinghss2110 |
C#
static void selectionSort(node head) { node temp = head; // Traverse the List while (temp) { node min = temp; node r = temp.next; // Traverse the unsorted sublist while (r) { if (min.data > r.data) min = r; r = r.next; } // Swap Data int x = temp.data; temp.data = min.data; min.data = x; temp = temp.next; } } // This code contributed by shivanisinghss2110 |
Javascript
<script> function selectionSort(head) { var temp = head; // Traverse the List while (temp) { var min = temp; var r = temp.next; // Traverse the unsorted sublist while (r) { if (min.data > r.data) min = r; r = r.next; } // Swap Data var x = temp.data; temp.data = min.data; min.data = x; temp = temp.next; } } </script> |
Python3
def selectionSort(head): temp = head # Traverse the List while (temp): minn = temp r = temp.next # Traverse the unsorted sublist while (r): if (minn.data > r.data): minn = r r = r.next # Swap Data x = temp.data temp.data = minn.data minn.data = x temp = temp.next # This code is contributed by shubhamsingh10 |
Method 2: Data swapping is no doubt easier to implement and understand, but in some cases( as one mentioned above ), it isn’t desirable. While doing swapping of the next parts of two nodes, four cases are needed to be taken into consideration :
- Nodes are adjacent and the first node is the starting node.
- Nodes are adjacent and the first node isn’t the starting node.
- Nodes aren’t adjacent and the first node is the starting node.
- Nodes aren’t adjacent and the first node isn’t the starting node.
Below is the implementation of the above approach:
C++
// C++ implementation of the approach #include <bits/stdc++.h> using namespace std; // Linked List Node struct Node { int data; Node* next; }; // Utility function to create a // new Linked List Node Node* newNode(int val) { Node* temp = new Node; temp->data = val; temp->next = NULL; return temp; } // Function to sort a linked list using selection // sort algorithm by swapping the next pointers Node* selectionSort(Node* head) { Node *a, *b, *c, *d, *r; a = b = head; // While b is not the last node while (b->next) { c = d = b->next; // While d is pointing to a valid node while (d) { if (b->data > d->data) { // If d appears immediately after b if (b->next == d) { // Case 1: b is the head of the linked list if (b == head) { // Move d before b b->next = d->next; d->next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Update the head head = b; // Skip to the next element // as it is already in order d = d->next; } // Case 2: b is not the head of the linked list else { // Move d before b b->next = d->next; d->next = b; a->next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d->next; } } // If b and d have some non-zero // number of nodes in between them else { // Case 3: b is the head of the linked list if (b == head) { // Swap b->next and d->next r = b->next; b->next = d->next; d->next = r; c->next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d->next; // Update the head head = b; } // Case 4: b is not the head of the linked list else { // Swap b->next and d->next r = b->next; b->next = d->next; d->next = r; c->next = b; a->next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d->next; } } } else { // Update c and skip to the next element // as it is already in order c = d; d = d->next; } } a = b; b = b->next; } return head; } // Function to print the list void printList(Node* head) { while (head) { cout << head->data << " "; head = head->next; } } // Driver Code int main() { Node* head = newNode(5); head->next = newNode(4); head->next->next = newNode(3); head = selectionSort(head); printList(head); return 0; } |
Java
// Java implementation of the approach class GFG { // Linked List Node static class Node { int data; Node next; }; // Utility function to create a // new Linked List Node static Node newNode(int val) { Node temp = new Node(); temp.data = val; temp.next = null; return temp; } // Function to sort a linked list using selection // sort algorithm by swapping the next pointers static Node selectionSort(Node head) { Node a, b, c, d, r; a = b = head; // While b is not the last node while (b.next != null) { c = d = b.next; // While d is pointing to a valid node while (d != null) { if (b.data > d.data) { // If d appears immediately after b if (b.next == d) { // Case 1: b is the head of the linked list if (b == head) { // Move d before b b.next = d.next; d.next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Update the head head = b; // Skip to the next element // as it is already in order d = d.next; } // Case 2: b is not the head of the linked list else { // Move d before b b.next = d.next; d.next = b; a.next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; } } // If b and d have some non-zero // number of nodes in between them else { // Case 3: b is the head of the linked list if (b == head) { // Swap b.next and d.next r = b.next; b.next = d.next; d.next = r; c.next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; // Update the head head = b; } // Case 4: b is not the head of the linked list else { // Swap b.next and d.next r = b.next; b.next = d.next; d.next = r; c.next = b; a.next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; } } } else { // Update c and skip to the next element // as it is already in order c = d; d = d.next; } } a = b; b = b.next; } return head; } // Function to print the 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 = newNode(5); head.next = newNode(4); head.next.next = newNode(3); head = selectionSort(head); printList(head); } } // This code is contributed by Arnab Kundu |
Python3
# Python3 implementation of the approach # Linked List Node class Node: def __init__(self, val): self.data = val self.next = None # Function to sort a linked list # using selection sort algorithm # by swapping the next pointers def selectionSort(head): a = b = head # While b is not the last node while b.next: c = d = b.next # While d is pointing to a valid node while d: if b.data > d.data: # If d appears immediately after b if b.next == d: # Case 1: b is the head # of the linked list if b == head: # Move d before b b.next = d.next d.next = b # Swap b and d pointers b, d = d, b c = d # Update the head head = b # Skip to the next element # as it is already in order d = d.next # Case 2: b is not the head # of the linked list else: # Move d before b b.next = d.next d.next = b a.next = d # Swap b and d pointers b, d = d, b c = d # Skip to the next element # as it is already in order d = d.next # If b and d have some non-zero # number of nodes in between them else: # Case 3: b is the head # of the linked list if b == head: # Swap b.next and d.next r = b.next b.next = d.next d.next = r c.next = b # Swap b and d pointers b, d = d, b c = d # Skip to the next element # as it is already in order d = d.next # Update the head head = b # Case 4: b is not the head # of the linked list else: # Swap b.next and d.next r = b.next b.next = d.next d.next = r c.next = b a.next = d # Swap b and d pointers b, d = d, b c = d # Skip to the next element # as it is already in order d = d.next else: # Update c and skip to the next element # as it is already in order c = d d = d.next a = b b = b.next return head # Function to print the list def printList(head): while head: print(head.data, end = " ") head = head.next # Driver Code if __name__ == "__main__": head = Node(5) head.next = Node(4) head.next.next = Node(3) head = selectionSort(head) printList(head) # This code is contributed # by Rituraj Jain |
C#
// C# implementation of the approach using System; class GFG { // Linked List Node public class Node { public int data; public Node next; }; // Utility function to create a // new Linked List Node static Node newNode(int val) { Node temp = new Node(); temp.data = val; temp.next = null; return temp; } // Function to sort a linked list using selection // sort algorithm by swapping the next pointers static Node selectionSort(Node head) { Node a, b, c, d, r; a = b = head; // While b is not the last node while (b.next != null) { c = d = b.next; // While d is pointing to a valid node while (d != null) { if (b.data > d.data) { // If d appears immediately after b if (b.next == d) { // Case 1: b is the head of the linked list if (b == head) { // Move d before b b.next = d.next; d.next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Update the head head = b; // Skip to the next element // as it is already in order d = d.next; } // Case 2: b is not the head of the linked list else { // Move d before b b.next = d.next; d.next = b; a.next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; } } // If b and d have some non-zero // number of nodes in between them else { // Case 3: b is the head of the linked list if (b == head) { // Swap b.next and d.next r = b.next; b.next = d.next; d.next = r; c.next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; // Update the head head = b; } // Case 4: b is not the head of the linked list else { // Swap b.next and d.next r = b.next; b.next = d.next; d.next = r; c.next = b; a.next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; } } } else { // Update c and skip to the next element // as it is already in order c = d; d = d.next; } } a = b; b = b.next; } return head; } // Function to print the list static void printList(Node head) { while (head != null) { Console.Write(head.data + " "); head = head.next; } } // Driver Code public static void Main(String[] arg) { Node head = newNode(5); head.next = newNode(4); head.next.next = newNode(3); head = selectionSort(head); printList(head); } } // This code contributed by Rajput-Ji |
Javascript
<script> // Javascript implementation of the approach // Structure of a node of linked list class Node { constructor() { this.data = 0; this.next = null; } } // Utility function to create a // new Linked List Node function newNode( val) { var temp = new Node(); temp.data = val; temp.next = null; return temp; } // Function to sort a linked list using selection // sort algorithm by swapping the next pointers function selectionSort( head) { var a, b, c, d, r; a = b = head; // While b is not the last node while (b.next != null) { c = d = b.next; // While d is pointing to a valid node while (d != null) { if (b.data > d.data) { // If d appears immediately after b if (b.next == d) { // Case 1: b is the head of the linked list if (b == head) { // Move d before b b.next = d.next; d.next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Update the head head = b; // Skip to the next element // as it is already in order d = d.next; } // Case 2: b is not the head of the linked list else { // Move d before b b.next = d.next; d.next = b; a.next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; } } // If b and d have some non-zero // number of nodes in between them else { // Case 3: b is the head of the linked list if (b == head) { // Swap b.next and d.next r = b.next; b.next = d.next; d.next = r; c.next = b; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; // Update the head head = b; } // Case 4: b is not the head of the linked list else { // Swap b.next and d.next r = b.next; b.next = d.next; d.next = r; c.next = b; a.next = d; // Swap b and d pointers r = b; b = d; d = r; c = d; // Skip to the next element // as it is already in order d = d.next; } } } else { // Update c and skip to the next element // as it is already in order c = d; d = d.next; } } a = b; b = b.next; } return head; } // Function to print the list function printList( head) { while (head != null) { document.write(head.data + " "); head = head.next; } } // Driver Code var head = newNode(5); head.next = newNode(4); head.next.next = newNode(3); head = selectionSort(head); printList(head); // This code is contributed by jana_sayantan. </script> |
Output:
3 4 5
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