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:

C++

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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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Python3

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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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Output:

125 3 100 6 15 5


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Improved By : Ryuga