找规律题的机械方法！
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
析：一个数在连续经过这个过程会变化到哪些数？ 例如， n=12,依次出现 12 5 25 29 85 89 145 42 20 4 16 37 58 89 145 42 20 4 16 37 n=15,依次出现 15 26 40 16 37 58 89 145 42 20 4 16 37 58 89 145 42 20 4 16 n=666,依次出现 666 108 65 61 37 58 89 145 42 20 4 16 37 58 89 145 42 20 4 16
猜想，一个数经过若干次运算，总会出现1或4，其中4会陷入死循环
// 自己在对多个数据连续输出测试时发现，经过有限次的运算总是会出现1或4，其中4会出现死循环 public boolean isHappy(int n) { while(n>0){ if(n==1) return true; if(n==4) return false; n = getSquareSum(n); } return true; } public int getSquareSum(int n){ int sum=0; while(n>0){ sum+= (n%10)*(n%10); n/=10; } return sum; }