LeetCode - Happy Number

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LeetCode 的 Happy Number 題目如下：

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


簡單說他是要一個功能，當數值帶入可判別數值是否 happy number。

Happy number 為一個正整數，將數值的每個位數平方後相加，反覆這樣的邏輯，最後的數值會為 1。

舉個例子來說，19為 happy number：

1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

筆者的解法： 

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public class Solution {
    public bool IsHappy(int n) {
        var value = n;
        do
        {
            var newValue = 0;
            foreach(var c in value.ToString())
            {
                newValue += (int)Math.Pow(c - '0', 2);
            }
            value = newValue;
        }while(value >= 10);
        return value == 1;
    }
}