Nested for loops — Question 19
Back to all questionsQuestion 8
Write a program to determine if an entered number is a Happy Number. A happy number is defined by the following process:
Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number is equal to 1.
For example, 19 is a happy number, as per the following calculation:
12 + 92 = 82,
82 + 22 = 68,
62 + 82 = 100,
12 + 02 + 02 = 1
import java.util.Scanner;
public class KboatHappyNumber
{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter number to check: ");
long num = in.nextLong();
long sum = 0;
long n = num;
do {
sum = 0;
while (n != 0) {
int d = (int)(n % 10);
sum += d * d;
n /= 10;
}
n = sum;
} while (sum > 6);
if (sum == 1) {
System.out.println(num + " is a Happy Number");
}
else {
System.out.println(num + " is not a Happy Number");
}
}
}Output
Key Concepts Covered
This question tests your understanding of the following concepts from the chapter Nested for loops: Question, Program, Determine, Entered, Number, Happy. These are fundamental topics in Computer Applications that students are expected to master as part of the ICSE Class 10 curriculum.
A thorough understanding of these concepts will help you answer similar questions confidently in your ICSE examinations. These topics are frequently tested in both objective and subjective sections of Computer Applications papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This Question
Read the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to Remember
- Write programs with proper indentation and comments.
- Trace through your code with sample inputs to verify correctness.
- Explain the logic behind each step of your solution.
- Familiarise yourself with common library functions and methods.
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