From 818bfab5d7ecf7b9340a408d5441de3ef6ae771e Mon Sep 17 00:00:00 2001
From: Tovi Jaeschke-Rogers <tovi.jaeschke-rogers@four.io>
Date: Thu, 3 Nov 2022 19:20:24 +1030
Subject: [PATCH] Add roman numeral to int converter (with validity checking)

---
 romanToInt.php | 165 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 165 insertions(+)
 create mode 100644 romanToInt.php

diff --git a/romanToInt.php b/romanToInt.php
new file mode 100644
index 0000000..531d65f
--- /dev/null
+++ b/romanToInt.php
@@ -0,0 +1,165 @@
+<?php
+
+class Solution {
+    const romanToIntMap = [
+        'M' => 1000,
+        'D' => 500,
+        'C' => 100,
+        'L' => 50,
+        'X' => 10,
+        'V' => 5,
+        'I' => 1,
+    ];
+
+    /**
+     * @param mixed $str
+     * @static
+     * @access public
+     * @return int
+     */
+    public static function romanToInt(string $str, $checkInvalid = false): int
+    {
+        if ($checkInvalid && !self::isRomanValid($str)) {
+            throw new RuntimeException('Given number is invalid');
+        }
+
+        $total = 0;
+
+        $letters = str_split(strtoupper($str));
+
+        for ($i = 0; $i < count($letters); $i++) {
+            $letterVal = self::romanToIntMap[$letters[$i]];
+            $nextLetterVal = isset($letters[$i + 1]) ? self::romanToIntMap[$letters[$i + 1]] : 0;
+
+            if ($letterVal < $nextLetterVal) {
+                $total -= $letterVal;
+                continue;
+            }
+
+            $total += $letterVal;
+        }
+
+        return $total;
+    }
+
+    /**
+     * @param string $str
+     * @static
+     * @access public
+     * @return bool
+     */
+    public static function isRomanValid(string $str): bool
+    {
+        // If an empty string is provided, return false,
+        // as the romans did not have a concept of 0
+        // (btw, they called it "nulla")
+        if ($str === '') {
+            return false;
+        }
+
+        $letters = str_split(strtoupper($str));
+
+        $currentLetter = $letters[0];
+        $count = 0;
+
+        for ($i = 1; $i < count($letters); $i++) {
+
+            // Ensure V, L, and D are not repeated, and
+            // if I, X, and C are the only subtractive operators
+            $letterVal = self::romanToIntMap[$currentLetter];
+            $nextLetterVal = isset($letters[$i]) ? self::romanToIntMap[$letters[$i]] : 0;
+            $currentVal = substr($letterVal, 0, 1);
+            if ($letterVal <= $nextLetterVal && ($currentVal === '5' || $nextLetterVal === '1000')) {
+                return false;
+            }
+
+            // Check if a number is repeated more than 3 times
+            $letterSameAsNext = $currentLetter === $letters[$i];
+            $count = $letterSameAsNext ? $count + 1 : 0;
+            if ($count >= 3) {
+                return false;
+            }
+
+
+            $currentLetter = $letters[$i] ?? '';
+        }
+
+        return true;
+    }
+
+    /**
+     * @param mixed $str
+     * @param mixed $expectedVal
+     * @static
+     * @access public
+     * @return void
+     */
+    public static function testRomanToInt(string $str, int $expectedVal): void
+    {
+        $val = self::romanToInt($str);
+        if ($val != $expectedVal) {
+            echo sprintf(
+                'Failed: The value of \'%d\' did not match the expected value of \'%d\' for \'%s\'' . PHP_EOL,
+                $val,
+                $expectedVal,
+                $str
+            );
+            return;
+        }
+
+        echo sprintf(
+            'Succeeded: The value of \'%d\' matched the expected value of \'%s\'' . PHP_EOL,
+            $val,
+            $str
+        );
+    }
+
+    /**
+     * @param string $str
+     * @param bool $expectedValid
+     * @static
+     * @access public
+     * @return void
+     */
+    public static function testIsRomanValid(string $str, bool $expectedValid) {
+        $val = self::isRomanValid($str);
+        if ($val != $expectedValid) {
+            echo sprintf(
+                'Failed: The value of \'%s\' did not match the expected value of \'%s\' for \'%s\'' . PHP_EOL,
+                $val ? 'True' : 'False',
+                $expectedValid ? 'True' : 'False',
+                $str
+            );
+            return;
+        }
+
+        echo sprintf(
+            'Succeeded: The value of \'%d\' matched the expected value of \'%s\'' . PHP_EOL,
+            $val ? 'True' : 'False',
+            $str
+        );
+
+    }
+}
+
+// Tests
+Solution::testRomanToInt('I', 1);
+Solution::testRomanToInt('III', 3);
+Solution::testRomanToInt('IV', 4);
+Solution::testRomanToInt('V', 5);
+Solution::testRomanToInt('VI', 6);
+Solution::testRomanToInt('IX', 9);
+Solution::testRomanToInt('X', 10);
+Solution::testRomanToInt('XI', 11);
+Solution::testRomanToInt('LVIII', 58);
+Solution::testRomanToInt('MCMXCIV', 1994);
+
+// Validity tests
+Solution::testIsRomanValid('III', true);
+Solution::testIsRomanValid('IIII', false);
+Solution::testIsRomanValid('VI', true);
+Solution::testIsRomanValid('VV', false);
+Solution::testIsRomanValid('LL', false);
+Solution::testIsRomanValid('VL', false);
+Solution::testIsRomanValid('DD', false);
+Solution::testIsRomanValid('MCMXCIV', true);