Search⌘ K
AI Features
Home
Courses
Grokking the Coding Interview Patterns in Python

Happy Number

Explore the fast and slow pointer method to check if a number is a happy number by repeatedly summing the squares of its digits. Understand how to detect cycles efficiently within this process. This lesson equips you to solve cycle detection problems relevant to coding interviews and improve your problem-solving skills.

We'll cover the following...

Statement

Write an algorithm to determine if a number nn is a happy number.

We use the following process to check if a given number is a happy number:

  • Starting with the given number nn, replace the number with the sum of the squares of its digits.
  • Repeat the process until:
    • The number equals 11, which will depict that the given number nn is a happy number.
    • The number enters a cycle, which will depict that the given number nn is not a happy number.

Return TRUE if nn is a happy number, and FALSE if not.

Constraints

  • 1≤1 \leq nn ≤231−1\leq 2^{31} - 1

Examples

canvasAnimation-image
1 / 2

Understand the problem

Let’s take a moment to make sure we have correctly understood the problem. The quiz below helps us to check that we are solving precisely the right problem:

Happy Number

1.

(True or False) 28 is a happy number.

A.

True

B.

False

1 / 2

Figure it out

We have a game for you to play: re-arrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to re-arrange them in the correct sequence.
1
2
3
4
5

Try it yourself

Implement your solution in the following coding playground.

Python
usercode > main.py
def is_happy_number(n):



    # Replace this placeholder return statement with your code

    return False
Happy Number