leetcode解题之202 # Happy Number Java版 （开心数）

202. Happy Number

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
• 题目大意
  

  　　对任意一个正整数，不断求个数位上数字的平方和，若最终收敛为1，则该数字为happy number，否则程序可能从某个数开始陷入循环。
  

  
  解题思路
  　　对这个数字的每个数位求平方和，如果如和为1或者平方和是之前出现过的就不进行求和，根据最后的结果判断是不是一个开心数字。

public  boolean isHappy(int n) {if (n == 0)return false;if (n == 1)return true;int temp = 0;//set 储存中间的结果Set<Integer> set=new HashSet<>();while (n != 1) {if (set.contains(n))return false;set.add(n);while (n != 0) {temp=temp+(n%10)*(n%10);n /= 10;}n = temp;temp=0;}return true;}