hanCodeHub

3/13/2020 - 6:31 PM

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.

```
public boolean isHappy(int n) {
if (n == 0) return false;
if (n == 1) return true;
HashSet<Integer> set = new HashSet<>();
int total = 0;
while (n != 1) {
// chop digits and add to total
while (n >= 1) {
total += Math.pow(n % 10, 2);
n /= 10;
}
// if cycling back to same num
if (set.contains(total)) {
return false;
}
set.add(total);
// repeat next num with total
n = total;
total = 0;
}
// num reaches 1
return true;
}
```