[LeetCode202] 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 and replace the number by the Sum of the squares of its digits, and repeat the process until the number equals 1 (where it would stay), or it loops Endl essly in a cycle which does not include 1. Those numbers for which this process ends in 1 is happy numbers.

Example: is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

Solution:

Use loop to calcuate the square sum until meet one of the these of the stops:

1. Sum is 1, return true

2. Sum value got before, which means there is a sum loop and would never goes to 1. return False

public boolean ishappy (int n) {        if (n<=0) return false;        Set<long> records = new hashset<> ();        Long ln = n;        while (ln< integer.max_value) {            if (records.contains (LN)) return false;            else Records.add (LN);            ln = getsquaresum (LN);            if (ln = = 1) return true;        }        return false;    }    Public long getsquaresum (long N) {        long sum = 0;        while (n!=0) {            sum+= Math.pow (n%10,2);            n/=10;        }        return sum;    }

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[LeetCode202] Happy number