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++
// 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 notbool 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 notvoid 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 arrayvoid 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 Codeint main()
{ int arr[] = { 2, 5, 10, 15, 17, 21, 23 };
int n = sizeof(arr) / sizeof(arr[0]);
// Function call
Print(arr, n);
return 0;
} |
Java
// Java program to print the prime numbers in the // first half and second half of an arrayimport java.util.*;
class GFG
{// Function to check if // a number is prime or notstatic 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 notstatic 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 arraystatic 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 Codepublic 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 |
Python3
# 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 notdef 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 notdef 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 arraydef 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 Codearr = [2, 5, 10, 15, 17, 21, 23]
n = len(arr)
# Function callPrint(arr, n)
# This code is contributed # by Mohit Kumar |
C#
// C# program to print the prime numbers in the // first half and second half of an arrayusing System;
class GFG
{// Function to check if // a number is prime or notstatic 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 notstatic 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 arraystatic 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 Codepublic 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 |
Javascript
<script>// Javascript 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 notfunction prime(n)
{ for (let i = 2; i * i <= n; i++)
if (n % i == 0)
return false;
return true;
}// Function to find whether elements are prime or notfunction prime_range(start, end, a)
{ // Traverse in the given range
for (let i = start; i < end; i++) {
// Check if a number is prime or not
if (prime(a[i]))
document.write(a[i] + " ");
}
}// Function to print the prime numbers in the// first half and second half of an arrayfunction Print(arr, n)
{ document.write("Prime numbers in the first half are ");
prime_range(0, parseInt(n / 2), arr);
document.write("<br>");
document.write("Prime numbers in the second half are ");
prime_range(parseInt(n / 2), n, arr);
document.write("<br>");
}// Driver Codelet arr = [ 2, 5, 10, 15, 17, 21, 23 ];let n = arr.length;// Function callPrint(arr, n);// This code is contributed by rishavmahato348.</script> |
Output:
Prime numbers in the first half are 2 5 Prime numbers in the second half are 17 23
Time Complexity: O(n * sqrt(n)), as we are using a loop for traversing n times and each time for checking if a number is prime or not we are using a loop to traverse sqrt(n) times which will cost O(sqrt(n)).
Auxiliary Space: O(1), as we are not using any extra space.