<?php

/*

* 用字母表数字替换字符串的字母

* In this kata you are required to, given a string, replace every letter with its position in the alphabet.

* If anything in the text isn't a letter, ignore it and don't return it.

* As an example:

alphabet_position('The sunset sets at twelve o\' clock.');

Should return "20 8 5 19 21 14 19 5 20 19 5 20 19 1 20 20 23 5 12 22 5 15 3 12 15 3 11" as a string.

*/

function alphabet_position(string $s): string

{

// 字母表数组

$letterArr = [1 => 'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];

// 将参数$s全部小写, 转换为目标数组

$targetArr = str_split(strtolower($s));

$result = '';

// 循环目标数组

foreach ($targetArr as $value) {

// 循环字母表数组

foreach ($letterArr as $k=>$v) {

// 比较两个数组中值,若相等, 取出字母表数组中键

if ($value == $v) {

$result .= $k.' ';

}

}

}

// 去除右边空格.

return rtrim($result);

}

function alphabet_position_clever(string $s): string

{

$value = '';

// 根据正则表达式排除非字符的字符串, 转换为目标数组, 并循环

foreach(str_split(preg_replace('/[^a-z]/i', '', $s)) as $letter) {

// 求每个大写英文字符 ASCII 码值.

// A在ASCII表是第65,依次排序25个字母,所以要减去64得到26个字母表正确数字

// https://baike.baidu.com/pic/ASCII/309296/0/c2fdfc039245d688c56332adacc27d1ed21b2451?fr=lemma&ct=single#aid=0&pic=c2fdfc039245d688c56332adacc27d1ed21b2451

$letterToNumber = ord(strtoupper($letter)) - 64;

// 拼接字符串

$value .= " {$letterToNumber}";

}

return trim($value);

}