Rearrange all elements of array which are multiples of x in decreasing order

Given an array of integers arr[] and an integer x, the task is to sort all the elements of the array which are multiples of x in decreasing order in their relative positions i.e. positions of the other elements must not be affected.

Examples:

Input: arr[] = {10, 5, 8, 2, 15}, x = 5
Output: 15 10 8 2 5
We rearrange all multiples of 5 (i.e. 10, 5 and 15) in decreasing order in their relative positions, keeping other elements same.

Input: arr[] = {100, 12, 25, 50, 5}, x = 5
Output: 100 12 50 25 5

Approach:



  1. Traverse the array and check if the number is multiple of x. If it is, store it in a vector.
  2. Then, sort the vector in decreasing order.
  3. Again traverse the array and replace the elements which are multiples of 5 with the vector elements one by one.

Below is the implementation of the above approach:

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// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Function to sort all the
// multiples of x from the
// array in decreasing order
void sortMultiples(int arr[], int n, int x)
{
    vector<int> v;
  
    // Insert all multiples of x to a vector
    for (int i = 0; i < n; i++)
        if (arr[i] % x == 0)
            v.push_back(arr[i]);
  
    // Sort the vector in descending
    sort(v.begin(), v.end(), std::greater<int>());
  
    int j = 0;
  
    // update the array elements
    for (int i = 0; i < n; i++) {
        if (arr[i] % x == 0)
            arr[i] = v[j++];
    }
}
  
// Utility function to print the array
void printArray(int arr[], int N)
{
    // Print the array
    for (int i = 0; i < N; i++) {
        cout << arr[i] << " ";
    }
}
  
// Driver code
int main()
{
    int arr[] = { 125, 3, 15, 6, 100, 5 };
    int x = 5;
    int n = sizeof(arr) / sizeof(arr[0]);
  
    sortMultiples(arr, n, x);
  
    printArray(arr, n);
  
    return 0;
}
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// Java implementation of the approach
import java.util.*;
  
class GFG
{
  
    // Function to sort all the
    // multiples of x from the
    // array in decreasing order
    static void sortMultiples(int arr[], int n, int x) 
    {
        Vector<Integer> v = new Vector<Integer>();
  
        // Insert all multiples of x to a vector
        for (int i = 0; i < n; i++) 
        {
            if (arr[i] % x == 0
            {
                v.add(arr[i]);
            }
        }
  
        // Sort the vector in descending
        Collections.sort(v, Collections.reverseOrder());
  
        int j = 0;
  
        // update the array elements
        for (int i = 0; i < n; i++)
        {
            if (arr[i] % x == 0
            {
                arr[i] = v.get(j++);
            }
        }
    }
  
    // Utility function to print the array
    static void printArray(int arr[], int N)
    {
        // Print the array
        for (int i = 0; i < N; i++)
        {
            System.out.print(arr[i] + " ");
        }
    }
  
    // Driver code
    public static void main(String[] args) 
    {
        int arr[] = {125, 3, 15, 6, 100, 5};
        int x = 5;
        int n = arr.length;
  
        sortMultiples(arr, n, x);
  
        printArray(arr, n);
    }
}
  
// This code has been contributed by 29AjayKumar
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# Python3 implementation of the approach 
  
# Function to sort all the 
# multiples of x from the 
# array in decreasing order 
def sortMultiples(arr, n, x) :
    v = [] 
  
    # Insert all multiples of x 
    # to a vector 
    for i in range(n) : 
        if (arr[i] % x == 0) :
            v.append(arr[i]) 
  
    # Sort the vector in descending 
    v.sort(reverse = True)
    j = 0
  
    # update the array elements 
    for i in range(n) : 
        if (arr[i] % x == 0) :
            arr[i] = v[j]
            j += 1
              
# Utility function to print the array 
def printArray(arr, N) :
  
    # Print the array 
    for i in range(N) : 
        print(arr[i], end = " ")
  
# Driver code 
if __name__ == "__main__" :
  
    arr= [ 125, 3, 15, 6, 100, 5
    x = 5
    n = len(arr)
      
    sortMultiples(arr, n, x)
  
    printArray(arr, n) 
  
# This code is contributed by Ryuga
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// C# implementation of the approach
using System;
using System.Collections.Generic; 
  
class GFG
{
  
    // Function to sort all the
    // multiples of x from the
    // array in decreasing order
    static void sortMultiples(int []arr, int n, int x) 
    {
        List<int> v = new List<int>();
  
        // Insert all multiples of x to a vector
        for (int i = 0; i < n; i++) 
        {
            if (arr[i] % x == 0) 
            {
                v.Add(arr[i]);
            }
        }
  
        // Sort the vector in descending
        v.Sort();
        v.Reverse();
  
        int j = 0;
  
        // update the array elements
        for (int i = 0; i < n; i++)
        {
            if (arr[i] % x == 0) 
            {
                arr[i] = v[j++];
            }
        }
    }
  
    // Utility function to print the array
    static void printArray(int []arr, int N)
    {
        // Print the array
        for (int i = 0; i < N; i++)
        {
            Console.Write(arr[i] + " ");
        }
    }
  
    // Driver code
    public static void Main() 
    {
        int []arr = {125, 3, 15, 6, 100, 5};
        int x = 5;
        int n = arr.Length;
  
        sortMultiples(arr, n, x);
  
        printArray(arr, n);
    }
}
  
/* This code contributed by PrinciRaj1992 */
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<?php 
// PHP implementation of the approach
  
// Function to sort all the multiples 
// of x from the array in decreasing order
function sortMultiples(&$arr, $n, $x)
{
    $v = array();
  
    // Insert all multiples of x to a vector
    for ($i = 0; $i < $n; $i++)
        if ($arr[$i] % $x == 0)
            array_push($v, $arr[$i]);
  
    // Sort the vector in descending
    rsort($v);
  
    $j = 0;
  
    // update the array elements
    for ($i = 0; $i < $n; $i++) 
    {
        if ($arr[$i] % $x == 0)
            $arr[$i] = $v[$j++];
    }
}
  
// Utility function to print the array
function printArray($arr, $N)
{
    // Print the array
    for ($i = 0; $i < $N; $i++) 
    {
        echo $arr[$i] . " ";
    }
}
  
// Driver code
$arr = array(125, 3, 15, 6, 100, 5 );
$x = 5;
$n = sizeof($arr);
  
sortMultiples($arr, $n, $x);
  
printArray($arr, $n);
  
// This code is contributed by ita_c
?>
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Output:
125 3 100 6 15 5

Time Complexity : O(n)

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