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
Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.
public class Solution {public int GetSquareSum(int num){int sum = 0;while (num >= 1){if (num >= 10){sum += (num % 10) * (num % 10);}else{sum += num * num;}num = num/10;}return sum;}public bool IsHappy(int n){List<int> numberList = new List<int>();while (true){n = GetSquareSum(n);if (n == 1){return true;}else if (numberList.IndexOf(n) >= 0){return false;}numberList.Add(n);}}}
原文：http://www.cnblogs.com/xiejunzhao/p/f7bc4135e1a4a09d1e9034db83298e97.html