(java)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

思路:快樂數就是經過上述運算後結果為1，進入1=1的死循環。如果進入沒有1的死循環如 4 16=16； 1+36=37 9+49=58 25+64=89； 64+81=145； 1+16+25=42 16+4=20 4+0=4 ...... 進入循環4的死循環，不是快樂數。 代碼如下,已認證leetcode public class Solution {

   public boolean isHappy(int n) {

    List<Integer> list=new ArrayList<Integer>();

    list.add(n);

    int temp=n;

    boolean isrepeate=false;

       while(temp>0) {

        if(isrepeate) break;

        String strn=""+temp;

        temp=0;

        int length=strn.length();

        for(int i=0;i<length;i++) {

        temp+=(strn.charAt(i)-'0')*(strn.charAt(i)-'0');

        }

        Iterator<Integer> it=list.iterator();

        while(it.hasNext()) {

        if(temp==it.next()) {

        if(temp==1) return true;

        else {

        isrepeate=true;

        break;

        }

        } 

        }

        if(!isrepeate) list.add(temp);

       }

       return false;

   }

}