Find prime numbers in the first half and second half of an array

Given an array arr of size N. The task is to find the prime numbers in the first half (up to index N/2) and the second half (all the remaining elements) of an array.

Examples:

Input : arr[] = {2, 5, 10, 15, 17, 21, 23 }
Output :2 5 and 17 23
Prime numbers in the first half of an array are 2, 5 and in the second half are 17, 23



Input : arr[] = {31, 35, 40, 43}
Output :31 and 43

Approach:
First Traverse the array up to N/2 and check all the elements whether they are prime or not and print the prime numbers. Then Traverse the array from N/2th element till N and find whether elements are prime or not and print all those elements which are prime.

Below is the implementation of the above approach:

C++

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// C++ program to print the prime numbers in the 
// first half and second half of an array
#include <bits/stdc++.h>
using namespace std;
  
// Function to check if a number is prime or not
bool prime(int n)
{
    for(int i = 2; i*i <= n; i++)
        if(n%i==0)
            return false;
              
    return true;
}
  
  
// Function to find whether elements are prime or not
void prime_range(int start, int end, int* a)
{
    // Traverse in the given range
    for (int i = start; i < end; i++) 
    {
      
        // Check if a number is prime or not
        if(prime(a[i]))
            cout << a[i] << " ";
    }
}
  
  
// Function to print the prime numbers in the 
// first half and second half of an array
void Print(int arr[], int n)
{
  
    cout << "Prime numbers in the first half are ";
    prime_range(0, n / 2, arr);
    cout << endl;
  
    cout << "Prime numbers in the second half are ";
    prime_range(n / 2, n, arr);
    cout << endl;
}
  
// Driver Code
int main()
{
  
    int arr[] = { 2, 5, 10, 15, 17, 21, 23 };
  
    int n = sizeof(arr) / sizeof(arr[0]);
      
    // Function call
    Print(arr, n);
  
    return 0;
}

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Java

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// Java program to print the prime numbers in the 
// first half and second half of an array
import java.util.*;
  
class GFG 
{
  
// Function to check if 
// a number is prime or not
static boolean prime(int n)
{
    for(int i = 2; i * i <= n; i++)
        if(n % i == 0)
            return false;
              
    return true;
}
  
// Function to find whether elements
// are prime or not
static void prime_range(int start, 
                        int end, int[] a)
{
    // Traverse in the given range
    for (int i = start; i < end; i++) 
    {
      
        // Check if a number is prime or not
        if(prime(a[i]))
            System.out.print(a[i] + " ");
    }
}
  
  
// Function to print the prime numbers in the 
// first half and second half of an array
static void Print(int arr[], int n)
{
  
    System.out.print("Prime numbers in the first half are ");
    prime_range(0, n / 2, arr);
    System.out.println();
  
    System.out.print("Prime numbers in the second half are ");
    prime_range(n / 2, n, arr);
    System.out.println();
}
  
// Driver Code
public static void main(String[] args) 
{
    int arr[] = { 2, 5, 10, 15, 17, 21, 23 };
  
    int n = arr.length;
      
    // Function call
    Print(arr, n);
}
}
  
// This code is contributed by Princi Singh

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Python3

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# Python3 program to print the 
# prime numbers in the first half 
# and second half of an array
  
# Function to check if 
# a number is prime or not
def prime(n):
  
    for i in range(2, n):
        if i * i > n:
            break
        if(n % i == 0):
            return False;
  
    return True
      
# Function to find whether 
# elements are prime or not
def prime_range(start, end, a):
      
    # Traverse in the given range
    for i in range(start, end):
  
        # Check if a number is prime or not
        if(prime(a[i])):
            print(a[i], end = " ")
  
# Function to print the 
# prime numbers in the first half
# and second half of an array
def Print(arr, n):
  
    print("Prime numbers in the",
          "first half are ", end = "")
    prime_range(0, n // 2, arr)
    print()
  
    print("Prime numbers in the"
          "second half are ", end = "")
    prime_range(n // 2, n, arr)
    print()
  
# Driver Code
arr = [2, 5, 10, 15, 17, 21, 23]
  
n = len(arr)
  
# Function call
Print(arr, n)
  
# This code is contributed 
# by Mohit Kumar

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C#

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// C# program to print the prime numbers in the 
// first half and second half of an array
using System;
      
class GFG 
{
  
// Function to check if 
// a number is prime or not
static Boolean prime(int n)
{
    for(int i = 2; i * i <= n; i++)
        if(n % i == 0)
            return false;
              
    return true;
}
  
// Function to find whether elements
// are prime or not
static void prime_range(int start, 
                        int end, int[] a)
{
    // Traverse in the given range
    for (int i = start; i < end; i++) 
    {
      
        // Check if a number is prime or not
        if(prime(a[i]))
            Console.Write(a[i] + " ");
    }
}
  
  
// Function to print the prime numbers in the 
// first half and second half of an array
static void Print(int []arr, int n)
{
  
    Console.Write("Prime numbers in the first half are ");
    prime_range(0, n / 2, arr);
    Console.WriteLine();
  
    Console.Write("Prime numbers in the second half are ");
    prime_range(n / 2, n, arr);
    Console.WriteLine();
}
  
// Driver Code
public static void Main(String[] args) 
{
    int []arr = { 2, 5, 10, 15, 17, 21, 23 };
  
    int n = arr.Length;
      
    // Function call
    Print(arr, n);
}
}
  
// This code is contributed by 29AjayKumar

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Output:

Prime numbers in the first half are 2 5
Prime numbers in the second half are 17 23


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