202. Happy Number

16 會壞掉，這題還要再改一下

class Solution {

    /**
     * @param Integer $n
     * @return Boolean
     */
    function isHappy($n) {
        if ($n < 5) {
            return $n === 1;
        }

        $targets = str_split($n);
        $result = 0;
        foreach($targets as $target) {
            $result += $target ** 2;
        }

        return $this->isHappy($result);
    }
}