[ LeetCode ] [ Kotlin ] - 202. Happy Number 難度 ★ (Kotlin速度第一名 )－西瓜是肥貓

先看看題目：

202. Happy Number

Easy

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

附上通關證明：

截圖 2020-08-19 下午3.26.17

我的想法：題目是說把數字拆成個位數，然後各自平方相加，如果出現結果是 1 的話就回傳true，如果重複的話就回傳 false，這題我就依照題目需求寫一個function，然後把結果存在map中，如果出現重複就結束迴圈，粗略寫了一下，意外拿到100%。

class Solution {
      fun isHappy(n: Int): Boolean {
         fun getNextNumber(n:Int):Int{
            var result = 0
            for(c in n.toString()){
                val cInt = Character.getNumericValue(c)
                val cN = if(cInt!=0) (cInt*cInt) else 0
                result += cN
            }
            return result
        }
        val map = HashMap<Int,Boolean>()
        var nextN = n
        while(map[nextN]==null){
            map[nextN] = true
            nextN = getNextNumber(nextN)
            if(nextN==1)
                return true
        }
        return false
    }
}