Java: Find the number which has the maximum number of distinct prime factors in a given range

Java Math Exercises: Exercise-21 with Solution

Write a Java program to find the number with the maximum number of distinct prime factors in a given range.

Sample Solution:

Java Code:

import java.util.*;

public class solution {
    static int max_distinct_primes(int r1, int r2) 
{ 
    long factor_count[] = new long[r2 + 1]; 
    boolean prime_num[] = new boolean[r2 + 1]; 
    for (int i = 0; i <= r2; i++) 
    { 
        factor_count[i] = 0; 
        prime_num[i] = true;
    } 
  
    for (int i = 2; i <= r2; i++) 
    { 
        if (prime_num[i] == true)  
        { 
  
           factor_count[i] = 1; 
           for (int j = i * 2; j <= r2; j += i)  
            { 
                factor_count[j]++; 
                prime_num[j] = false; 
            } 
        } 
    } 
 
    int max_num = (int)factor_count[r1]; 
    int num = r1; 
  
    for (int i = r1; i <= r2; i++) 
      {   
        if (factor_count[i] > max_num) 
        { 
            max_num = (int)factor_count[i]; 
            num = i; 
        } 
    } 
    return num; 
} 
  
   public static void main(String[] args) {
       Scanner scan = new Scanner(System.in);
       System.out.print("Input first integer: ");
       int num1 = scan.nextInt();
       System.out.print("Input second integer: ");
       int num2 = scan.nextInt();
       scan.close(); 
	   if (num1>0 && num2>0 && num2>num1)
	   {
          System.out.println("Maximum number of distinct prime factors of the said range: "+max_distinct_primes(num1, num2));		
	   }
		}
}

Sample Output:

Input first integer:  5
Input second integer:  25
Maximum number of distinct prime factors of the said range: 6

Flowchart:

Java Code Editor:

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