Perfect Number Program in Java Using While Loop
The number which is equal to the sum of its divisors is called a perfect number. Read the entered long number, assigned to the long variable n. While loop iterates until the condition (i<=n/2) is false. If the remainder of n/i=0 then add i value to the sum and increase the i value. After all the iterations compare the number with the sum, if both are equal then prints the number as a perfect number.
Example:
n = 6, i = 1 condition at while is 1 <= 3 is true, here 6%i = 0 is true so sum = 1,
i = 2, 2 < 3 is true, 6%2 = 0 is true so sum = 1+2=3,
i=3, 3<=3 is true, 6%3=0 is true so sum=3+3=6, for i=4 the while loop terminates and compares the sum value with n, both are equal, so it prints 6 is a perfect number.
Implementation
Java
import java.util.Scanner;class Perfect{ public static void main(String arg[]) { long n,sum=0; Scanner sc=new Scanner(System.in); System.out.println("Enter a number"); n=sc.nextLong(); int i=1; while(i<=n/2) { if(n%i==0) { sum+=i; } i++; } if(sum==n) { System.out.println(n+" is a perfect number"); } else System.out.println(n+" is not a perfect number"); }} |
Output:
The time complexity is O(n), where n is the input number.
The auxiliary space is O(1)
Example :
Java
import java.io.*;public class PerfectNumber { public static void main(String[] args) { int number = 1; while (number <= 10000) { int sum = 0; // Find all the factors of the current number and add them up for (int i = 1; i < number; i++) { if (number % i == 0) { sum += i; } } // If the sum of the factors equals the number, it's a perfect number if (sum == number) { System.out.println(number + " is a perfect number"); } number++; } }} |
output :
6 is a perfect number 28 is a perfect number 496 is a perfect number 8128 is a perfect number
