202. Happy Number

**问题描述：

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

1^2 + 9^2 = 82

8^2 + 2^2 = 68

6^2 + 8^2 = 100

1^2 + 0^2 + 0^2 = 1**

下面附代码:

public class Solution {
public boolean isHappy(int n) {
int num=n;
boolean[] a = new boolean[]{false,true,false,false,false,false,false,true,false,false};
while(num>9){
int sum=0;
while(num>0){
sum+=Math.pow(num%10,2);
num/=10;
}
num=sum;
}
if(num==1){
return true;
}
return a[num];
}
}

某位大牛的代码：

public boolean isHappy(int n) {
if(n<=0) return false;
while(true){
int sum=0;
while(n!=0){
sum+=(n%10)*(n%10);
n=n/10;
}
if(sum/10==0){
if(sum==1||sum==7) return true;
else return false;
}
n=sum;
}
}