Happy Number (medium)

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Happy Number (medium)

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Problem Statement

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Problem Statement

Any number will be called a happy number if, after repeatedly replacing it with a number equal to the sum of the square of all of its digits, leads us to the number 1. All other (not-happy) numbers will never reach 1. Instead, they will be stuck in a cycle of numbers that does not include 1.

Given a positive number n, return true if it is a happy number otherwise return false.

Example 1:

Input: 23
Output: true (23 is a happy number)
Explanations: Here are the steps to find out that 23 is a happy number:

$2^2 +3^2$ = 4 + 9 = 13
$1^2 + 3^2$ = 1 + 9 = 10
$1^2 + 0^2$ = 1 + 0 = 1

Example 2:

Input: 12
Output: false (12 is not a happy number)
Explanations: Here are the steps to find out that 12 is not a happy number:

$1^2 +2^2$ = 1 + 4 = 5
$5^2$ = 25
$2^2 + 5^2$ = 4 + 25 = 29
$2^2 + 9^2$ = 4 + 81 = 85
$8^2 + 5^2$ = 64 + 25 = 89
$8^2 + 9^2$ = 64 + 81 = 145
$1^2 + 4^2 + 5^2$ = 1 + 16 + 25 = 42
$4^2 + 2^2$ = 16 + 4 = 20
$2^2 + 0^2$ = 4 + 0 = 4
$4^2$ = 16
$1^2 + 6^2$ = 1 + 36 = 37
$3^2 + 7^2$ = 9 + 49 = 58
$5^2 + 8^2$ = 25 + 64 = 89

Please note the cycle from 89 -> 89.

Constraints:

1 <= n <= 2<sup>31</sup> - 1

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Python3

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Problem Statement

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