SumOfDigitsOfStringAfterConvert.php

<?php

namespace App;

/**
 * Sum of Digits of String After Convert
 *
 * You are given a string s consisting of lowercase English letters, and an integer k. First, convert s into an integer
 * by replacing each letter with its position in the alphabet (i.e., replace 'a' with 1, 'b' with 2, ..., 'z' with 26).
 * Then, transform the integer by replacing it with the sum of its digits. Repeat the transform operation k times in
 * total. For example, if s = "zbax" and k = 2, then the resulting integer would be 8 by the following operations:
 * - Convert: "zbax" ➝ "(26)(2)(1)(24)" ➝ "262124" ➝ 262124
 * - Transform #1: 262124 ➝ 2 + 6 + 2 + 1 + 2 + 4 ➝ 17
 * - Transform #2: 17 ➝ 1 + 7 ➝ 8
 * Return the resulting integer after performing the operations described above.
 *
 * Example 1:
 * Input: s = "iiii", k = 1
 * Output: 36
 * Explanation: The operations are as follows:
 * - Convert: "iiii" ➝ "(9)(9)(9)(9)" ➝ "9999" ➝ 9999
 * - Transform #1: 9999 ➝ 9 + 9 + 9 + 9 ➝ 36
 * Thus the resulting integer is 36.
 *
 * Example 2:
 * Input: s = "leetcode", k = 2
 * Output: 6
 * Explanation: The operations are as follows:
 * - Convert: "leetcode" ➝ "(12)(5)(5)(20)(3)(15)(4)(5)" ➝ "12552031545" ➝ 12552031545
 * - Transform #1: 12552031545 ➝ 1 + 2 + 5 + 5 + 2 + 0 + 3 + 1 + 5 + 4 + 5 ➝ 33
 * - Transform #2: 33 ➝ 3 + 3 ➝ 6
 * Thus the resulting integer is 6.
 *
 * https://leetcode.com/problems/sum-of-digits-of-string-after-convert
 */
class SumOfDigitsOfStringAfterConvert
{
    /**
     * @param string $str
     * @param int $k
     * @return int
     */
    function getLucky(string $str, int $k): int
    {
        $alphabet = range('a', 'z');
        $str = str_replace($alphabet, range(1, 26), $str);
        $sum = array_sum(str_split($str));
        for ($i = 1; $i < $k; $i++) {
            $sum = array_sum(str_split((string) $sum));
        }
        return (int) $sum;
    }
}