202. Happy Number | LeetCode | Top Interview 150 | Coding Questions

Problem Link

https://leetcode.com/problems/happy-number/

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Detailed Step-by-Step Explanation

https://leetcode.com/problems/happy-number/solutions/7498157/most-optimal-solution-beats-5000-hashmap-ozqv

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Solution

class Solution {
    public boolean isHappy(int n) {

        Set<Integer> usedInteger = new HashSet<>();

        while (n != 1 && !usedInteger.contains(n)) {
            usedInteger.add(n);

            int sum = 0;
            while (n > 0) {
                int digit = n % 10;
                sum += digit * digit;
                n = n / 10;
            }

            n = sum;
        }

        return n == 1;
    }
}