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Happy Number

Explore the fast and slow pointer technique to identify happy numbers efficiently by detecting cycles in the sum of squared digits. Learn to implement and analyze this algorithm to determine if a number eventually leads to 1 or enters a cycle, mastering a common coding interview pattern.

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

  • 11 \leq nn 2311\leq 2^{31} - 1

Examples

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Test your understanding of 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


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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.

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Try it yourself

Implement your solution in the following coding playground.

JavaScript
usercode > main.js
export function isHappyNumber(n) {
// Replace this placeholder return statement with your code
return false;
}
Happy Number