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++
// 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; } |
Java
// 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 |
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 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 |
C#
// 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 |
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 not function 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 not function 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 array function 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 Code let arr = [ 2, 5, 10, 15, 17, 21, 23 ]; let n = arr.length; // Function call Print(arr, n); // This code is contributed by rishavmahato348. </script> |
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.