<?php

/**

* [solution description] 转化为罗马数字

* @param [type] $roman [description]

* @return [type] [description]

*/

function solution ($roman) {

$number = 0;

$symbolArr = [

'I' => 1,

'V' => 5,

'X' => 10,

'L' => 50,

'C' => 100,

'D' => 500,

'M' => 1000,

];

// 循环字符串

for ($i = 0; $i < strlen($roman); $i++) {

// 对应字符串的字符在罗马数组的值

$value = $symbolArr[$roman[$i]];

// 若$i 等于 该字符串的最后一个或者 $i后一个的值小于当前的值则相加

if ($i == strlen($roman) - 1 || $symbolArr[$roman[$i + 1]] <= $value) {

$number += $value;

} else { // 否则减去 排除如 CD, XC这种情况

$number -= $value;

}

}

return $number;

}

function solution_clever ($roman) {

$number = 0;

$numerals = array("CM" => 900, "M" => 1000, "CD" => 400, "D" => 500, "XC" => 90, "C" => 100, "XL" => 40, "L" => 50, "IX" => 9, "X" => 10, "IV" => 4, "V" => 5, "I" => 1);

foreach ($numerals as $numeral => $value) {

// 通过str_replace 统计字符串的出现次数

$roman = str_replace($numeral, "", $roman, $count);

// 根据次数来计算

$number += $count * $value;

}

return $number;

}