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;
}