202. Happy number

subject ：

Write an algorithm to judge a number n Is it a happy number .

「 Happy number 」 Defined as ： For a positive integer , Replace the number with the sum of the squares of the numbers in each of its positions , Then repeat the process until the number becomes 1, It could be Infinite loop But it doesn't change 1. If It can be   1, So this number is the happy number .

If n If it's happy, count it back True ; No , Then return to False .

Ideas ：

Each calculated sum recorded , If there are repeated sum You can judge that you can't get the number of happiness , If there is no repetition sum value , Then it means that this calculation will continue until we find sum=1;

public class Kuaileshu {
    // Take the sum of the squares of the singular numbers of each digit 
    public int getSum(int n){
        int sum = 0;
        while(n>0){
            sum +=(n%10)*(n%10);
            n/=10;
        }
        return sum;
    }

    public boolean isHappy(int n){
        Set<Integer> record = new HashSet<>();
        // If the sum of squares is not equal to 1 And there is no sum of squares in the set 
        // Put the sum of this square into the set 
        while( n!= 1 && !record.contains(n)){
            record.add(n);
            n = getSum(n);
        }
        return n==1;
    }

    public static void main(String[] args) {
        Kuaileshu kuaileshu = new Kuaileshu();
        boolean res = kuaileshu.isHappy(19);
        System.out.println(res);
    }
}

Output results ： 

True