Ordenar los números primos de una array en orden descendente

Dada una array de enteros ‘arr’, la tarea es clasificar todos los números primos de la array en orden descendente en sus posiciones relativas, es decir, otras posiciones de los otros elementos no deben verse afectadas.
Ejemplos: 
 

Input: arr[] = {2, 5, 8, 4, 3}
Output: 5 3 8 4 2

Input: arr[] = {10, 12, 2, 6, 5}
Output: 10 12 5 6 2

Acercarse: 
 

• Crea un tamiz para comprobar si un elemento es primo o no en O(1).
• Recorre la array y comprueba si el número es primo. Si es primo, guárdelo en un vector.
• Luego, ordena el vector en orden descendente.
• Recorra nuevamente la array y reemplace los números primos con los elementos del vector uno por uno.

A continuación se muestra la implementación del enfoque anterior:
 

// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
bool prime[100005];
 
void SieveOfEratosthenes(int n)
{
 
    memset(prime, true, sizeof(prime));
 
    // false here indicates
    // that it is not prime
    prime[1] = false;
 
    for (int p = 2; p * p <= n; p++) {
 
        // If prime[p] is not changed,
        // then it is a prime
        if (prime[p]) {
 
            // Update all multiples of p,
            // set them to non-prime
            for (int i = p * 2; i <= n; i += p)
                prime[i] = false;
        }
    }
}
 
// Function that sorts
// all the prime numbers
// from the array in descending
void sortPrimes(int arr[], int n)
{
    SieveOfEratosthenes(100005);
 
    // this vector will contain
    // prime numbers to sort
    vector<int> v;
 
    for (int i = 0; i < n; i++) {
 
        // if the element is prime
        if (prime[arr[i]])
            v.push_back(arr[i]);
    }
 
    sort(v.begin(), v.end(), greater<int>());
 
    int j = 0;
 
    // update the array elements
    for (int i = 0; i < n; i++) {
        if (prime[arr[i]])
            arr[i] = v[j++];
    }
}
 
// Driver code
int main()
{
 
    int arr[] = { 4, 3, 2, 6, 100, 17 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    sortPrimes(arr, n);
 
    // print the results.
    for (int i = 0; i < n; i++) {
        cout << arr[i] << " ";
    }
 
    return 0;
}

// Java implementation of the approach
import java.util.*;
 
class GFG
{
 
    static boolean prime[] = new boolean[100005];
 
    static void SieveOfEratosthenes(int n)
    {
 
        Arrays.fill(prime, true);
 
        // false here indicates
        // that it is not prime
        prime[1] = false;
 
        for (int p = 2; p * p <= n; p++)
        {
 
            // If prime[p] is not changed,
            // then it is a prime
            if (prime[p]) {
 
                // Update all multiples of p,
                // set them to non-prime
                for (int i = p * 2; i < n; i += p)
                {
                    prime[i] = false;
                }
            }
        }
    }
 
    // Function that sorts
    // all the prime numbers
    // from the array in descending
    static void sortPrimes(int arr[], int n)
    {
        SieveOfEratosthenes(100005);
 
        // this vector will contain
        // prime numbers to sort
        Vector<Integer> v = new Vector<Integer>();
 
        for (int i = 0; i < n; i++)
        {
 
            // if the element is prime
            if (prime[arr[i]])
            {
                v.add(arr[i]);
            }
        }
        Comparator comparator = Collections.reverseOrder();
        Collections.sort(v, comparator);
 
        int j = 0;
 
        // update the array elements
        for (int i = 0; i < n; i++)
        {
            if (prime[arr[i]])
            {
                arr[i] = v.get(j++);
            }
        }
    }
 
    // Driver code
    public static void main(String[] args)
    {
        int arr[] = {4, 3, 2, 6, 100, 17};
        int n = arr.length;
 
        sortPrimes(arr, n);
 
        // print the results.
        for (int i = 0; i < n; i++)
        {
            System.out.print(arr[i] + " ");
        }
    }
}
 
// This code is contributed by 29AjayKumar

# Python3 implementation of the approach
 
def SieveOfEratosthenes(n):
 
    # false here indicates
    # that it is not prime
    prime[1] = False
    p = 2
    while p * p <= n:
 
        # If prime[p] is not changed,
        # then it is a prime
        if prime[p]:
 
            # Update all multiples of p,
            # set them to non-prime
            for i in range(p * 2, n + 1, p):
                prime[i] = False
         
        p += 1
 
# Function that sorts all the prime
# numbers from the array in descending
def sortPrimes(arr, n):
 
    SieveOfEratosthenes(100005)
 
    # This vector will contain
    # prime numbers to sort
    v = []
    for i in range(0, n):
 
        # If the element is prime
        if prime[arr[i]]:
            v.append(arr[i])
 
    v.sort(reverse = True)
    j = 0
 
    # update the array elements
    for i in range(0, n):
        if prime[arr[i]]:
            arr[i] = v[j]
            j += 1
             
    return arr
     
# Driver code
if __name__ == "__main__":
 
    arr = [4, 3, 2, 6, 100, 17]
    n = len(arr)
     
    prime = [True] * 100006
    arr = sortPrimes(arr, n)
 
    # print the results.
    for i in range(0, n):
        print(arr[i], end = " ")
     
# This code is contributed by Rituraj Jain

// C# implementation of the approach
using System;
using System.Collections.Generic;
 
class GFG
{
 
    static bool []prime = new bool[100005];
 
    static void SieveOfEratosthenes(int n)
    {
 
        for(int i = 0; i < 100005; i++)
            prime[i] = true;
 
        // false here indicates
        // that it is not prime
        prime[1] = false;
 
        for (int p = 2; p * p <= n; p++)
        {
 
            // If prime[p] is not changed,
            // then it is a prime
            if (prime[p])
            {
 
                // Update all multiples of p,
                // set them to non-prime
                for (int i = p * 2; i < n; i += p)
                {
                    prime[i] = false;
                }
            }
        }
    }
 
    // Function that sorts
    // all the prime numbers
    // from the array in descending
    static void sortPrimes(int []arr, int n)
    {
        SieveOfEratosthenes(100005);
 
        // this vector will contain
        // prime numbers to sort
        List<int> v = new List<int>();
 
        for (int i = 0; i < n; i++)
        {
 
            // if the element is prime
            if (prime[arr[i]])
            {
                v.Add(arr[i]);
            }
        }
        v.Sort();
        v.Reverse();
 
        int j = 0;
 
        // update the array elements
        for (int i = 0; i < n; i++)
        {
            if (prime[arr[i]])
            {
                arr[i] = v[j++];
            }
        }
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        int []arr = {4, 3, 2, 6, 100, 17};
        int n = arr.Length;
 
        sortPrimes(arr, n);
 
        // print the results.
        for (int i = 0; i < n; i++)
        {
            Console.Write(arr[i] + " ");
        }
    }
}
 
// This code contributed by Rajput-Ji

<script>
 
// Javascript implementation of the approach
 
var prime = Array(100005).fill(true);
 
function SieveOfEratosthenes( n)
{
 
    // false here indicates
    // that it is not prime
    prime[1] = false;
 
    for (var p = 2; p * p <= n; p++) {
 
        // If prime[p] is not changed,
        // then it is a prime
        if (prime[p]) {
 
            // Update all multiples of p,
            // set them to non-prime
            for (var i = p * 2; i <= n; i += p)
                prime[i] = false;
        }
    }
}
 
// Function that sorts
// all the prime numbers
// from the array in descending
function sortPrimes(arr, n)
{
    SieveOfEratosthenes(100005);
 
    // this vector will contain
    // prime numbers to sort
    var v = [];
 
    for (var i = 0; i < n; i++) {
 
        // if the element is prime
        if (prime[arr[i]])
            v.push(arr[i]);
    }
 
    v.sort((a,b)=>b-a)
 
    var j = 0;
 
    // update the array elements
    for (var i = 0; i < n; i++) {
        if (prime[arr[i]])
            arr[i] = v[j++];
    }
}
 
// Driver code
var arr = [4, 3, 2, 6, 100, 17 ];
var n = arr.length;
sortPrimes(arr, n);
// print the results.
for (var i = 0; i < n; i++) {
    document.write( arr[i] + " ");
}
 
 
</script>

4 17 3 6 100 2