166. Happy Number

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Example 1:

Input: n = 19

Output: true

Explanation: 1^2 + 9^2 = 82 -> 8^2 + 2^2 = 68 -> 6^2 + 8^2 = 100 -> 1^2 + 0^2 + 0^2 = 1. Hence, 19 is a happy number.

Example 2:

Input: n = 2

Output: false

Explanation: The sequence loops endlessly without reaching 1: 2 -> 4 -> 16 -> 37 -> 58 -> 89 -> 145 -> 42 -> 20 -> 4. Since 4 has already been visited, a cycle is detected.

Constraints:

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Time Complexity

O(log n)

Space Complexity