024 - For Loop 6 (optional)

 

Using a for loop, determine whether the integer variable max is prime or not. If the number is prime, print out "prime". If it's not, print out "not prime". Keep in mind that 1 is NOT a prime number.

You can use the following to find the square root of a number (you may or may not use this):

Math.sqrt(num)

 

Sample input/outputs:

In: 100 out: not prime   In: 17 out: prime   In: 9 out: not prime   In: 1 out: not prime

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Solution

import java.util.*;
 
 
class Bakjoon {
  public static void main(String[] args) {
    Scanner inp = new Scanner(System.in);
    System.out.print("In:");
    double max = inp.nextDouble();
    //write your code below
    int sw=0;
    if(max==1||max==2) {
        System.out.println(max==2?"Prime":"not Prime");
         }
    else {
        if(max%2==0) {
            System.out.println("not Prime");
        }
        else {
            for(int i=3;i<=Math.sqrt(max);i++) {
                if(max%i==0) {
                    sw=1;
                }      
            }
            if(sw==1) {
                System.out.println("not Prime");
            }
            else {
                System.out.println("Prime");
            }
        }
    }
    
  }
}