Given a linked list which is sorted, how will you insert in sorted way - GeeksforGeeks

18 Feb, 2022
Given a sorted linked list and a value to insert, write a function to insert the value in a sorted way.Initial Linked List  
Linked List after insertion of 9  
 
 
Algorithm: Let input linked list is sorted in increasing order.  
1) If Linked list is empty then make the node as
   head and return it.
2) If the value of the node to be inserted is smaller 
   than the value of the head node, then insert the node 
at the start and make it head.
3) In a loop, find the appropriate node after 
   which the input node (let 9) is to be inserted. 
   To find the appropriate node start from the head, 
   keep moving until you reach a node GN (10 in
   the below diagram) who's value is greater than 
   the input node. The node just before GN is the
appropriate node (7).
4) Insert the node (9) after the appropriate node
   (7) found in step 3.
Implementation:  
C++
C
Java
Python
C#
Javascript
/* Program to insert in a sorted list */#include <bits/stdc++.h>using namespace std; /* Link list node */class Node {public:    int data;    Node* next;}; /* function to insert a new_nodein a list. Note that thisfunction expects a pointer tohead_ref as this can modify thehead of the input linked list(similar to push())*/void sortedInsert(Node** head_ref,                  Node* new_node){    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 JUSTUTILITY TO TEST sortedInsert */ /* A utility function tocreate a new node */Node* newNode(int new_data){    /* allocate node */    Node* new_node = new Node();     /* put in the data */    new_node->data = new_data;    new_node->next = NULL;     return new_node;} /* Function to print linked list */void printList(Node* head){    Node* temp = head;    while (temp != NULL) {        cout << temp->data << " ";        temp = temp->next;    }} /* Driver program to test count function*/int main(){    /* Start with the empty list */    Node* head = NULL;    Node* new_node = newNode(5);    sortedInsert(&head, new_node);    new_node = newNode(10);    sortedInsert(&head, new_node);    new_node = newNode(7);    sortedInsert(&head, new_node);    new_node = newNode(3);    sortedInsert(&head, new_node);    new_node = newNode(1);    sortedInsert(&head, new_node);    new_node = newNode(9);    sortedInsert(&head, new_node);    cout << "Created Linked List\n";    printList(head);     return 0;}// This is code is contributed by rathbhupendra
/* Program to insert in a sorted list */#include <stdio.h>#include <stdlib.h> /* Link list node */struct Node {    int data;    struct Node* next;}; /* function to insert a new_node in a list. Note that this  function expects a pointerto head_ref as this can modify the  head of the input linkedlist (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 beforethe 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 */ /* A utility function to create a new node */struct Node* newNode(int new_data){    /* allocate node */    struct Node* new_node= (struct Node*)malloc(sizeof(struct Node));     /* put in the data  */    new_node->data = new_data;    new_node->next = NULL;     return new_node;} /* Function to print linked list */void printList(struct Node* head){    struct Node* temp = head;    while (temp != NULL) {        printf("%d  ", temp->data);        temp = temp->next;    }} /* Driver program to test count function*/int main(){    /* Start with the empty list */    struct Node* head = NULL;    struct Node* new_node = newNode(5);    sortedInsert(&head, new_node);    new_node = newNode(10);    sortedInsert(&head, new_node);    new_node = newNode(7);    sortedInsert(&head, new_node);    new_node = newNode(3);    sortedInsert(&head, new_node);    new_node = newNode(1);    sortedInsert(&head, new_node);    new_node = newNode(9);    sortedInsert(&head, new_node);    printf("\n Created Linked List\n");    printList(head);     return 0;}
// Java Program to insert in a sorted listclass LinkedList {    Node head; // head of list     /* Linked list Node*/    class Node {        int data;        Node next;        Node(int d)        {            data = d;            next = null;        }    }     /* function to insert anew_node in a list. */    void sortedInsert(Node new_node)    {        Node current;         /* Special case for head node */        if (head == null || head.data>= new_node.data) {            new_node.next = head;            head = new_node;        }        else {             /* Locate the node before point of insertion. */            current = head;             while (current.next != null&& current.next.data < new_node.data)                current = current.next;             new_node.next = current.next;            current.next = new_node;        }    }     /*Utility functions*/     /* Function to create a node */    Node newNode(int data)    {        Node x = new Node(data);        return x;    }     /* Function to print linked list */    void printList()    {        Node temp = head;        while (temp != null) {            System.out.print(temp.data + " ");            temp = temp.next;        }    }     /* Driver function to test above methods */    public static void main(String args[])    {        LinkedList llist = new LinkedList();        Node new_node;        new_node = llist.newNode(5);        llist.sortedInsert(new_node);        new_node = llist.newNode(10);        llist.sortedInsert(new_node);        new_node = llist.newNode(7);        llist.sortedInsert(new_node);        new_node = llist.newNode(3);        llist.sortedInsert(new_node);        new_node = llist.newNode(1);        llist.sortedInsert(new_node);        new_node = llist.newNode(9);        llist.sortedInsert(new_node);        System.out.println("Created Linked List");        llist.printList();    }}/* This code is contributed by Rajat Mishra */
# Python program to insert in a sorted list # Node classclass Node:     # Constructor to initialize the node object    def __init__(self, data):        self.data = data        self.next = None class LinkedList:     # Function to initialize head    def __init__(self):        self.head = None     def sortedInsert(self, new_node):                 # Special case for the empty linked list        if self.head is None:            new_node.next = self.head            self.head = new_node         # Special case for head at end        elif self.head.data >= new_node.data:            new_node.next = self.head            self.head = new_node         else :             # Locate the node before the point of insertion            current = self.head            while(current.next is not None and                 current.next.data < new_node.data):                current = current.next                         new_node.next = current.next            current.next = new_node     # Function to insert a new node at the beginning    def push(self, new_data):        new_node = Node(new_data)        new_node.next = self.head        self.head = new_node     # Utility function to print it the LinkedList    def printList(self):        temp = self.head        while(temp):            print temp.data,            temp = temp.next  # Driver programllist = LinkedList()new_node = Node(5)llist.sortedInsert(new_node)new_node = Node(10)llist.sortedInsert(new_node)new_node = Node(7)llist.sortedInsert(new_node)new_node = Node(3)llist.sortedInsert(new_node)new_node = Node(1)llist.sortedInsert(new_node)new_node = Node(9)llist.sortedInsert(new_node)print "Create Linked List"llist.printList() # This code is contributed by Nikhil Kumar Singh(nickzuck_007)
// C# Program to insert in a sorted listusing System; public class LinkedList {    Node head; // head of list     /* Linked list Node*/    class Node {        public int data;        public Node next;        public Node(int d)        {            data = d;            next = null;        }    }     /* function to insert a new_node in a list. */    void sortedInsert(Node new_node)    {        Node current;         /* Special case for head node */        if (head == null || head.data >= new_node.data) {            new_node.next = head;            head = new_node;        }        else {             /* Locate the node before            point of insertion. */            current = head;             while (current.next != null && current.next.data < new_node.data)                current = current.next;             new_node.next = current.next;            current.next = new_node;        }    }     /*Utility functions*/     /* Function to create a node */    Node newNode(int data)    {        Node x = new Node(data);        return x;    }     /* Function to print linked list */    void printList()    {        Node temp = head;        while (temp != null) {            Console.Write(temp.data + " ");            temp = temp.next;        }    }     /* Driver code */    public static void Main(String[] args)    {        LinkedList llist = new LinkedList();        Node new_node;         new_node = llist.newNode(5);        llist.sortedInsert(new_node);         new_node = llist.newNode(10);        llist.sortedInsert(new_node);         new_node = llist.newNode(7);        llist.sortedInsert(new_node);         new_node = llist.newNode(3);        llist.sortedInsert(new_node);         new_node = llist.newNode(1);        llist.sortedInsert(new_node);         new_node = llist.newNode(9);        llist.sortedInsert(new_node);         Console.WriteLine("Created Linked List");        llist.printList();    }} /* This code is contributed by 29AjayKumar */
<script>// javascript Program to insert in a sorted listvar head; // head of list     /* Linked list Node */     class Node {            constructor(val) {                this.data = val;                this.next = null;            }        }         /*     * function to insert a new_node in a list.     */    function sortedInsert( new_node) {        var current;         /* Special case for head node */        if (head == null || head.data >= new_node.data) {            new_node.next = head;            head = new_node;        } else {             /* Locate the node before point of insertion. */            current = head;             while (current.next != null && current.next.data < new_node.data)                current = current.next;             new_node.next = current.next;            current.next = new_node;        }    }     /* Utility functions */     /* Function to create a node */    function newNode(data) {         x = new Node(data);        return x;    }     /* Function to print linked list */    function printList() {         temp = head;        while (temp != null) {            document.write(temp.data + " ");            temp = temp.next;        }    }     /* Driver function to test above methods */        var new_node;        new_node = newNode(5);        sortedInsert(new_node);        new_node = newNode(10);        sortedInsert(new_node);        new_node = newNode(7);        sortedInsert(new_node);        new_node = newNode(3);        sortedInsert(new_node);        new_node = newNode(1);        sortedInsert(new_node);        new_node = newNode(9);        sortedInsert(new_node);        document.write("Created Linked List<br/>");        printList(); // This code is contributed by aashish1995</script>
Output: 
Created Linked List
1 3 5 7 9 10 
Complexity Analysis:  
Time Complexity: O(n). Only one traversal of the list is needed.
Auxiliary Space: O(1). No extra space is needed.
Shorter Implementation using double pointers: Thanks to Murat M Ozturk for providing this solution. Please see Murat M Ozturk’s comment below for complete function. The code uses double-pointer to keep track of the next pointer of the previous node (after which new node is being inserted).Note that below line in code changes current to have address of next pointer in a node.  
   current = &((*current)->next);
Also, note below comments.  
    /* Copies the value-at-address current to
      new_node's next pointer*/ 
    new_node->next = *current; 

    /* Fix next pointer of the node (using its address) 
       after which new_node is being inserted */ 
    *current = new_node;  
Time Complexity: O(n) References: http://cslibrary.stanford.edu/105/LinkedListProblems.pdf 
29AjayKumar
rathbhupendra
Akanksha_Rai
nidhi_biet
andrew1234
aashish1995
arorakashish0911
simmytarika5
Amazon
Insertion Sort
SAP Labs
Wipro
Linked List
Amazon
Wipro
SAP Labs
Linked List
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Comments
Old Comments
LinkedList in Java
Linked List vs Array
Queue - Linked List Implementation
Merge two sorted linked lists
Detect loop in a linked list
Find the middle of a given linked list
Implement a stack using singly linked list
Implementing a Linked List in Java using Class
Merge Sort for Linked Lists
Circular Linked List | Set 1 (Introduction and Applications)