Leetcode PHP题解--D70 784. Letter Case Permutation

<?php

class Solution {

​

    /**

     * @param String $S

     * @return String[]

     */

    function letterCasePermutation($S) {

        $all = [$S];

        $S = str_split($S);

        $alphabets = str_split('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ');

        $chars = array_intersect($S, $alphabets);

        foreach($chars as $key => $value){

            foreach($all as $newString){

                $newStringArray = str_split($newString);

                $newStringArray[$key] = strtolower($newStringArray[$key]);

                $all[] = implode($newStringArray);

​

                $newStringArray = str_split($newString);

                $newStringArray[$key] = strtoupper($newStringArray[$key]);

                $all[] = implode($newStringArray);

            }

        }

        $all = array_unique($all);

        sort($all);

        return $all;

    }

}