MinimumMovesToConvertString.php

<?php

namespace App;

/**
 * Minimum Moves to Convert String
 *
 * You are given a string s consisting of n characters which are either 'X' or 'O'. A move is defined as selecting three
 * consecutive characters of s and converting them to 'O'. Note that if a move is applied to the character 'O', it will
 * stay the same. Return the minimum number of moves required so that all the characters of s are converted to 'O'.
 *
 * Example 1:
 * Input: s = "XXX"
 * Output: 1
 * Explanation: XXX -> OOO
 * We select all the 3 characters and convert them in one move.
 *
 * Example 2:
 * Input: s = "XXOX"
 * Output: 2
 * Explanation: XXOX -> OOOX -> OOOO
 * We select the first 3 characters in the first move, and convert them to 'O'.
 * Then we select the last 3 characters and convert them so that the final string contains all 'O's.
 *
 * Example 3:
 * Input: s = "OOOO"
 * Output: 0
 * Explanation: There are no 'X's in s to convert.
 *
 * https://leetcode.com/problems/minimum-moves-to-convert-string
 */
class MinimumMovesToConvertString
{
    /**
     * @param string $str
     * @return int
     */
    public function minimumMoves(string $str): int
    {
        $moves = 0;
        $i = 0;
        while ($i < strlen($str)) {
            if ($str[$i] === 'X') {
                $moves++;
                $i += 3;
            } else {
                $i++;
            }
        }
        return $moves;
    }
}