We have discussed Insertion Sort for arrays. In this article same for linked list is discussed.
Below is simple insertion sort algorithm for linked list.
1) Create an empty sorted (or result) list 2) Traverse the given list, do following for every node. ......a) Insert current node in sorted way in sorted or result list. 3) Change head of given linked list to head of sorted (or result) list.
The main step is (2.a) which has been covered in below post.
Sorted Insert for Singly Linked List
Below is implementation of above algorithm
C++
/* C program for insertion sort on a linked list */#include<stdio.h> #include<stdlib.h> /* Link list node */struct Node { int data; struct Node* next; }; // Function to insert a given node in a sorted linked list void sortedInsert(struct Node**, struct Node*); // function to sort a singly linked list using insertion sort void insertionSort(struct Node **head_ref) { // Initialize sorted linked list struct Node *sorted = NULL; // Traverse the given linked list and insert every // node to sorted struct Node *current = *head_ref; while (current != NULL) { // Store next for next iteration struct Node *next = current->next; // insert current in sorted linked list sortedInsert(&sorted, current); // Update current current = next; } // Update head_ref to point to sorted linked list *head_ref = sorted; } /* function to insert a new_node in a list. Note that this function expects a pointer to head_ref as this can modify the head of the input linked list (similar to push())*/void sortedInsert(struct Node** head_ref, struct Node* new_node) { struct Node* current; /* Special case for the head end */ if (*head_ref == NULL || (*head_ref)->data >= new_node->data) { new_node->next = *head_ref; *head_ref = new_node; } else { /* Locate the node before the point of insertion */ current = *head_ref; while (current->next!=NULL && current->next->data < new_node->data) { current = current->next; } new_node->next = current->next; current->next = new_node; } } /* BELOW FUNCTIONS ARE JUST UTILITY TO TEST sortedInsert */ /* Function to print linked list */void printList(struct Node *head) { struct Node *temp = head; while(temp != NULL) { printf("%d ", temp->data); temp = temp->next; } } /* A utility function to insert a node at the beginning of linked list */void push(struct Node** head_ref, int new_data) { /* allocate node */ struct Node* new_node = new Node; /* put in the data */ new_node->data = new_data; /* link the old list off the new node */ new_node->next = (*head_ref); /* move the head to point to the new node */ (*head_ref) = new_node; } // Driver program to test above functions int main() { struct Node *a = NULL; push(&a, 5); push(&a, 20); push(&a, 4); push(&a, 3); push(&a, 30); printf("Linked List before sorting
"); printList(a); insertionSort(&a); printf("
Linked List after sorting
"); printList(a); return 0; } |
Java
// Java program to sort link list // using insertion sort public class LinkedlistIS { node head; node sorted; class node { int val; node next; public node(int val) { this.val = val; } } void push(int val) { /* allocate node */ node newnode = new node(val); /* link the old list off the new node */ newnode.next = head; /* move the head to point to the new node */ head = newnode; } // function to sort a singly linked list using insertion sort void insertionSort(node headref) { // Initialize sorted linked list sorted = null; node current = headref; // Traverse the given linked list and insert every // node to sorted while (current != null) { // Store next for next iteration node next = current.next; // insert current in sorted linked list sortedInsert(current); // Update current current = next; } // Update head_ref to point to sorted linked list head = sorted; } /* * function to insert a new_node in a list. Note that * this function expects a pointer to head_ref as this * can modify the head of the input linked list * (similar to push()) */ void sortedInsert(node newnode) { /* Special case for the head end */ if (sorted == null || sorted.val >= newnode.val) { newnode.next = sorted; sorted = newnode; } else { node current = sorted; /* Locate the node before the point of insertion */ while (current.next != null && current.next.val < newnode.val) { current = current.next; } newnode.next = current.next; current.next = newnode; } } /* Function to print linked list */ void printlist(node head) { while (head != null) { System.out.print(head.val + " "); head = head.next; } } // Driver program to test above functions public static void main(String[] args) { LinkedlistIS list = new LinkedlistIS(); list.push(5); list.push(20); list.push(4); list.push(3); list.push(30); System.out.println("Linked List before Sorting.."); list.printlist(list.head); list.insertionSort(list.head); System.out.println("
LinkedList After sorting"); list.printlist(list.head); } } // This code is contributed by Rishabh Mahrsee |
C#
// C# program to sort link list // using insertion sort using System; public class LinkedlistIS { public node head; public node sorted; public class node { public int val; public node next; public node(int val) { this.val = val; } } void push(int val) { /* allocate node */ node newnode = new node(val); /* link the old list off the new node */ newnode.next = head; /* move the head to point to the new node */ head = newnode; } // function to sort a singly // linked list using insertion sort void insertionSort(node headref) { // Initialize sorted linked list sorted = null; node current = headref; // Traverse the given // linked list and insert every // node to sorted while (current != null) { // Store next for next iteration node next = current.next; // insert current in sorted linked list sortedInsert(current); // Update current current = next; } // Update head_ref to point to sorted linked list head = sorted; } /* * function to insert a new_node in a list. Note that * this function expects a pointer to head_ref as this * can modify the head of the input linked list * (similar to push()) */ void sortedInsert(node newnode) { /* Special case for the head end */ if (sorted == null || sorted.val >= newnode.val) { newnode.next = sorted; sorted = newnode; } else { node current = sorted; /* Locate the node before the point of insertion */ while (current.next != null && current.next.val < newnode.val) { current = current.next; } newnode.next = current.next; current.next = newnode; } } /* Function to print linked list */ void printlist(node head) { while (head != null) { Console.Write(head.val + " "); head = head.next; } } // Driver code public static void Main(String[] args) { LinkedlistIS list = new LinkedlistIS(); list.push(5); list.push(20); list.push(4); list.push(3); list.push(30); Console.WriteLine("Linked List before Sorting.."); list.printlist(list.head); list.insertionSort(list.head); Console.WriteLine("
LinkedList After sorting"); list.printlist(list.head); } } // This code contributed by Rajput-Ji |
Output:
Linked List before sorting 30 3 4 20 5 Linked List after sorting 3 4 5 20 30
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