Java Program to Check If a Number is Neon Number or Not

Difficulty Level : Medium
Last Updated : 13 Jan, 2021

A neon number is a number where the sum of digits of the square of the number is equal to the number. The task is to check and print neon numbers in a range.

Illustration:

Case 1:

Input  : 9
Output : Given number  9 is Neon number

Explanation : square of 9=9*9=81;
              sum of digit of square : 8+1=9(which is equal to given number)


Case 2:

Input : 8
Output : Given number is not a Neon number
 
Explanation : square of 8=8*8=64
              sum of digit of square : 6+4=10(which is not equal to given number)

Algorithm :

First, find the square of the given number.
Find the sum of the digit of the square by using a loop.
The condition checksum is equal to the given number
1. Return true
2. Else return false.

Pseudo code : Square =n*n;
              while(square>0)
              {
              int r=square%10;
              sum+=r;
              square=square/10;
              }

Example:

Java

// Java Program to Check If a Number is Neon number or not 
  
// Importing java input/output library 
import java.io.*; 
  
class GFG { 
  
    // Method to check whether number is neon or not 
    // Boolean type 
    public static boolean checkNeon(int n) 
    { 
        // squarring the number to be checked 
        int square = n * n; 
  
        // Initializing current sum to 0 
        int sum = 0; 
  
        // If product is positive 
        while (square > 0) { 
  
            // Step 1: Find remainder 
            int r = square % 10; 
  
            // Add remainder to the current sum 
            sum += r; 
  
            // Drop last digit of the product 
            // and store the number 
            square = square / 10; 
        } 
  
        // Condition check 
        // Sum of digits of number obtained is 
        // equal to original number 
        if (sum == n) 
  
            // number is neon 
            return true; 
        else
  
            // numbe is not neon 
            return false; 
    } 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
        // Custom input 
        int n = 9; 
  
        // Calling above functon to check custom number or 
        // if user entered number via Scanner class 
        if (checkNeon(n)) 
  
            // Print number considered is neon 
            System.out.println("Given number " + n 
                               + " is Neon number"); 
        else
  
            // Print number considered is not neon 
            System.out.println("Given number " + n 
                               + " is not a Neon number"); 
    } 
}

Output

Given number 9 is Neon number

Time Complexit: O(l) where l is the number of the digit in the square of the given number

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