202. Happy Number --LeetCode Record

Write an algorithm to determine if a number 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.

Example: 19 is a happy number

12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

    var middle:[Int:Bool] = [:]    func isHappy(n: Int) -> Bool {        var n = n        if n == 1 {            return true        }        if middle[n] != nil {            return false        }        middle[n] = true        var nextN = 0        while n != 0 {            nextN += (n % 10) * (n % 10)            n = n / 10        }        return isHappy(nextN)    }