202. Happy Number

Update time

Write an algorithm to determine if a number n is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Return True if n is a happy number, and False if not.

**Example: **

Input: 19
Output: true
Explanation: 12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

# @lc code=start
using LeetCode
function ishappy(n::Int)::Bool
    while n != 1
        n == 4 && return false ## all loops must contain 4
        n = sum(digits(n) .^ 2)
    end
    return true
end
# @lc code=end

ishappy (generic function with 1 method)

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