Sort the linked list in the order of elements appearing in the array

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Given an array of size N and a Linked List where elements will be from the array but can also be duplicated, sort the linked list in the order, elements are appearing in the array. It may be assumed that the array covers all elements of the linked list.
arr[] =

list =

Sorted list =

Asked in Amazon

First, make a hash table that stores the frequencies of elements in linked list. Then, simply traverse list and for each element of arr[i] check the frequency in the hashtable and modify the data of list by arr[i] element upto its frequency and at last Print the list.

Implementation:

C++

// Efficient CPP program to sort given list in order
// elements are appearing in an array
#include <bits/stdc++.h>
using namespace std;
 
// Linked list node
struct Node {
    int data;
    struct Node* next;
};
 
// function prototype for printing the list
void printList(struct Node*);
 
// Function to insert a node at the
// beginning of the linked list
void push(struct Node** head_ref, int new_data)
{
    struct Node* new_node = new Node;
    new_node -> data = new_data;
    new_node -> next = *head_ref;
    *head_ref = new_node;
}
 
// function to print the linked list
void printList(struct Node* head)
{
    while (head != NULL) {
        cout << head -> data << " -> ";
        head = head -> next;
    }
}
 
// Function that sort list in order of appearing
// elements in an array
void sortlist(int arr[], int N, struct Node* head)
{
    // Store frequencies of elements in a
    // hash table.
    unordered_map<int, int> hash;
    struct Node* temp = head;
    while (temp) {        
        hash[temp -> data]++;
        temp = temp -> next;
    }
 
    temp = head;
  
    // One by one put elements in list according
    // to their appearance in array
    for (int i = 0; i < N; i++) {        
 
        // Update 'frequency' nodes with value 
        // equal to arr[i]
        int frequency = hash[arr[i]];
        while (frequency--) {
 
            // Modify list data as element 
            // appear in an array
            temp -> data = arr[i];
            temp = temp -> next;
        }
    }
}
 
// Driver Code
int main()
{
    struct Node* head = NULL;
    int arr[] = { 5, 1, 3, 2, 8 };
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // creating the linked list
    push(&head, 3);
    push(&head, 2);
    push(&head, 5);
    push(&head, 8);
    push(&head, 5);
    push(&head, 2);
    push(&head, 1);
 
    // Function call to sort the list in order
    // elements are appearing in an array
    sortlist(arr, N, head);
 
    // print the modified linked list
    cout << "Sorted List:" << endl;
    printList(head);
    return 0;
}

Java

// Efficient JAVA program to sort given list in order
// elements are appearing in an array
import java.util.*;
 
class GFG
{
 
// Linked list node
static class Node
{
    int data;
    Node next;
};
 
// Function to insert a node at the
// beginning of the linked list
static Node push(Node head_ref, int new_data)
{
    Node new_node = new Node();
    new_node.data = new_data;
    new_node.next = head_ref;
    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;
    }
}
 
// Function that sort list in order of appearing
// elements in an array
static void sortlist(int arr[], int N, Node head)
{
    // Store frequencies of elements in a
    // hash table.
    HashMap<Integer,Integer> hash = new HashMap<Integer,Integer>();
    Node temp = head;
    while (temp != null) 
    { 
        if(hash.containsKey(temp.data))
            hash.put(temp.data,hash.get(temp.data) + 1);
        else
            hash.put(temp.data,1);
        temp = temp.next;
    }
 
    temp = head;
 
    // One by one put elements in list according
    // to their appearance in array
    for (int i = 0; i < N; i++) 
    {     
 
        // Update 'frequency' nodes with value 
        // equal to arr[i]
        int frequency = hash.get(arr[i]);
        while (frequency-->0) 
        {
 
            // Modify list data as element 
            // appear in an array
            temp.data = arr[i];
            temp = temp.next;
        }
    }
}
 
// Driver Code
public static void main(String[] args)
{
    Node head = null;
    int arr[] = { 5, 1, 3, 2, 8 };
    int N = arr.length;
 
    // creating the linked list
    head = push(head, 3);
    head = push(head, 2);
    head = push(head, 5);
    head = push(head, 8);
    head = push(head, 5);
    head = push(head, 2);
    head = push(head, 1);
 
    // Function call to sort the list in order
    // elements are appearing in an array
    sortlist(arr, N, head);
 
    // print the modified linked list
    System.out.print("Sorted List:" +"\n");
    printList(head);
}
}
 
// This code is contributed by PrinciRaj1992

Python3

# Efficient Python3 program to sort given list in order
# elements are appearing in an array
 
# Linked list node
class Node:
    def __init__(self):
        self.data = 0
        self.next = None
 
# Function to insert a node at the
# beginning of the linked list
def push( head_ref, new_data):
 
    new_node = Node()
    new_node.data = new_data
    new_node.next = head_ref
    head_ref = new_node
    return head_ref
 
# function to print the linked list
def printList( head):
 
    while (head != None):
     
        print(head.data, end = "->")
        head = head.next
     
# Function that sort list in order of appearing
# elements in an array
def sortlist( arr, N, head):
 
    # Store frequencies of elements in a
    # hash table.
    hash = dict()
    temp = head
    while (temp != None) :
     
        hash[temp.data] = hash.get(temp.data, 0) + 1
        temp = temp.next
     
    temp = head
 
    # One by one put elements in list according
    # to their appearance in array
    for i in range(N): 
         
        # Update 'frequency' nodes with value 
        # equal to arr[i]
        frequency = hash.get(arr[i],0)
         
        while (frequency > 0) :
         
            frequency= frequency-1
            # Modify list data as element 
            # appear in an array
            temp.data = arr[i]
            temp = temp.next
         
# Driver Code
 
head = None
arr = [5, 1, 3, 2, 8 ]
N = len(arr)
 
# creating the linked list
head = push(head, 3)
head = push(head, 2)
head = push(head, 5)
head = push(head, 8)
head = push(head, 5)
head = push(head, 2)
head = push(head, 1)
 
# Function call to sort the list in order
# elements are appearing in an array
sortlist(arr, N, head)
 
# print the modified linked list
print("Sorted List:" )
printList(head)
 
 
# This code is contributed by Arnab Kundu

C#

// Efficient C# program to sort given list in order
// elements are appearing in an array
using System;
using System.Collections.Generic;
 
class GFG
{
 
// Linked list node
public class Node
{
    public int data;
    public Node next;
};
 
// Function to insert a node at the
// beginning of the linked list
static Node push(Node head_ref, int new_data)
{
    Node new_node = new Node();
    new_node.data = new_data;
    new_node.next = head_ref;
    head_ref = new_node;
    return head_ref;
}
 
// function to print the linked list
static void printList(Node head)
{
    while (head != null)
    {
        Console.Write(head.data + "->");
        head = head.next;
    }
}
 
// Function that sort list in order of appearing
// elements in an array
static void sortlist(int []arr, int N, Node head)
{
    // Store frequencies of elements in a
    // hash table.
    Dictionary<int, 
               int> hash = new Dictionary<int, 
                                          int>();
    Node temp = head;
    while (temp != null) 
    { 
        if(hash.ContainsKey(temp.data))
            hash[temp.data] = hash[temp.data] + 1;
        else
            hash.Add(temp.data, 1);
        temp = temp.next;
    }
    temp = head;
 
    // One by one put elements in list according
    // to their appearance in array
    for (int i = 0; i < N; i++) 
    {     
 
        // Update 'frequency' nodes with value 
        // equal to arr[i]
        int frequency = hash[arr[i]];
        while (frequency-->0) 
        {
 
            // Modify list data as element 
            // appear in an array
            temp.data = arr[i];
            temp = temp.next;
        }
    }
}
 
// Driver Code
public static void Main(String[] args)
{
    Node head = null;
    int []arr = { 5, 1, 3, 2, 8 };
    int N = arr.Length;
 
    // creating the linked list
    head = push(head, 3);
    head = push(head, 2);
    head = push(head, 5);
    head = push(head, 8);
    head = push(head, 5);
    head = push(head, 2);
    head = push(head, 1);
 
    // Function call to sort the list in order
    // elements are appearing in an array
    sortlist(arr, N, head);
 
    // print the modified linked list
    Console.Write("Sorted List:" + "\n");
    printList(head);
}
}
 
// This code is contributed by 29AjayKumar

Javascript

<script>
 
// Efficient Javascript program to sort given list in order
// elements are appearing in an array
 
// Linked list node
class Node
{
    constructor()
    {
        this.data = 0;
        this.next = null;
    }
};
 
// Function to insert a node at the
// beginning of the linked list
function push(head_ref, new_data)
{
    var new_node = new Node();
    new_node.data = new_data;
    new_node.next = head_ref;
    head_ref = new_node;
    return head_ref;
}
 
// function to print the linked list
function printList(head)
{
    while (head != null)
    {
        document.write(head.data + " -> ");
        head = head.next;
    }
}
 
// Function that sort list in order of appearing
// elements in an array
function sortlist( arr, N, head)
{
    // Store frequencies of elements in a
    // hash table.
    var hash = new Map();
    var temp = head;
    while (temp != null) 
    { 
        if(hash.has(temp.data))
            hash.set(temp.data, hash.get(temp.data)+1);
        else
            hash.set(temp.data, 1);
        temp = temp.next;
    }
    temp = head;
 
    // One by one put elements in list according
    // to their appearance in array
    for (var i = 0; i < N; i++) 
    {     
 
        // Update 'frequency' nodes with value 
        // equal to arr[i]
        var frequency = hash.get(arr[i]);
        while (frequency-->0) 
        {
 
            // Modify list data as element 
            // appear in an array
            temp.data = arr[i];
            temp = temp.next;
        }
    }
}
 
// Driver Code
var head = null;
var arr = [5, 1, 3, 2, 8];
var N = arr.length;
// creating the linked list
head = push(head, 3);
head = push(head, 2);
head = push(head, 5);
head = push(head, 8);
head = push(head, 5);
head = push(head, 2);
head = push(head, 1);
// Function call to sort the list in order
// elements are appearing in an array
sortlist(arr, N, head);
// print the modified linked list
document.write("Sorted List:" + "<br>");
printList(head);
 
 
</script>

Output

Sorted List:
5 -> 5 -> 1 -> 3 -> 2 -> 2 -> 8 ->

Time Complexity: O(n²).
Auxiliary Space: O(n)

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