init

.gitignore

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+/build/
+/vendor/
+/composer.lock

.travis.yml

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+language: php
+
+php:
+    - '7.0'
+    - '7.1'
+    - '7.2'
+    - '7.3'
+
+install:
+    - composer install
+
+before_script:
+    - mkdir -p build/logs
+
+script:
+    - composer phpcs
+    - composer phpmd
+    - composer phpcpd
+    - composer test
+
+after_script:
+    - php vendor/bin/coveralls -v

composer.json

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+{
+    "name": "gordonlesti/longest-common-subsequence",
+    "type": "library",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Gordon Lesti",
+            "email": "info@gordonlesti.com"
+        }
+    ],
+    "require": {
+        "php": ">=7.0"
+    },
+    "autoload": {
+        "psr-4": {
+            "GordonLesti\\LongestCommonSubsequence\\": "src"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "GordonLesti\\LongestCommonSubsequenceTest\\": "tests"
+        }
+    },
+    "require-dev": {
+        "phpunit/phpunit": "^6.5",
+        "phpmd/phpmd": "^2.7",
+        "sebastian/phpcpd": "^3.0",
+        "squizlabs/php_codesniffer": "^3.5",
+        "satooshi/php-coveralls": "^2.1"
+    },
+    "scripts": {
+        "test": "php vendor/bin/phpunit",
+        "phpcs": "php vendor/bin/phpcs",
+        "phpmd": "php vendor/bin/phpmd src/,tests/ text cleancode,codesize,controversial,design,naming,unusedcode",
+        "phpcpd": "php vendor/bin/phpcpd src/ tests/"
+    }
+}

phpcs.xml

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+<?xml version="1.0"?>
+<ruleset name="Levenshtein">
+    <description>The coding standard for LongestCommonSubsequence.</description>
+    <file>src/</file>
+    <file>tests/</file>
+    <arg name="extensions" value="php"/>
+    <rule ref="PSR2"/>
+</ruleset>

phpunit.xml.dist

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+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit bootstrap="vendor/autoload.php"
+         backupGlobals="false"
+         backupStaticAttributes="false"
+         colors="true"
+         verbose="true"
+         convertErrorsToExceptions="true"
+         convertNoticesToExceptions="true"
+         convertWarningsToExceptions="true"
+         processIsolation="false"
+         stopOnFailure="false">
+    <testsuites>
+        <testsuite name="LongestCommonSubseqence Test Suite">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+    <filter>
+        <whitelist>
+            <directory suffix=".php">src/</directory>
+        </whitelist>
+    </filter>
+    <logging>
+        <log type="junit" target="build/report.junit.xml"/>
+        <log type="coverage-html" target="build/coverage" charset="UTF-8" yui="true" highlight="true"/>
+        <log type="coverage-text" target="build/coverage.txt"/>
+        <log type="coverage-clover" target="build/logs/clover.xml"/>
+    </logging>
+</phpunit>

src/LongestCommonSubsequence.php

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+<?php
+declare(strict_types=1);
+
+namespace GordonLesti\LongestCommonSubsequence;
+
+class LongestCommonSubsequence
+{
+    /**
+     * Calculates the longest common subsequence of both strings and returns the
+     * length.
+     * @see https://en.wikipedia.org/wiki/Longest_common_subsequence_problem
+     *
+     * @param string $str1
+     * @param string $str2
+     * @return int
+     */
+    public static function lcs(string $str1, string $str2): int
+    {
+        $matrix = [];
+        $str1Array = self::multiByteStringToArray($str1);
+        $str2Array = self::multiByteStringToArray($str2);
+        $str1Length = count($str1Array);
+        $str2Length = count($str2Array);
+
+        $matrix[0] = array_fill(0, $str2Length + 1, 0);
+        for ($i = 0; $i < $str1Length; $i++) {
+            $row = [0];
+            for ($j = 0; $j < $str2Length; $j++) {
+                if ($str1Array[$i] === $str2Array[$j]) {
+                    $row[$j + 1] = $matrix[$i][$j] + 1;
+                    continue;
+                }
+                $row[$j + 1] = max(
+                    $matrix[$i][$j + 1],
+                    $row[$j]
+                );
+            }
+            $matrix[$i + 1] = $row;
+        }
+        return $matrix[$str1Length][$str2Length];
+    }
+
+    /**
+     * Splits a multibyte string into an array and returns it.
+     *
+     * @param string $str
+     * @return array
+     */
+    private static function multiByteStringToArray(string $str): array
+    {
+        $length = mb_strlen($str);
+        $array = [];
+        for ($i = 0; $i < $length; $i++) {
+            $array[$i] = mb_substr($str, $i, 1);
+        }
+        return $array;
+    }
+}

tests/LongestCommonSubsequenceTest.php

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+<?php
+declare(strict_types=1);
+
+namespace GordonLesti\LongestCommonSubsequenceTest;
+
+use GordonLesti\LongestCommonSubsequence\LongestCommonSubsequence;
+use PHPUnit\Framework\TestCase;
+
+class LongestCommonSubsequenceTest extends TestCase
+{
+    /**
+     * @param string $str1
+     * @param string $str2
+     * @param int $lcsLength
+     * @SuppressWarnings(PHPMD.StaticAccess)
+     * @dataProvider lcsProvider
+     */
+    public function testLcs(string $str1, string $str2, int $lcsLength)
+    {
+        $this->assertSame(
+            $lcsLength,
+            LongestCommonSubsequence::lcs($str1, $str2)
+        );
+    }
+
+    /**
+     * @return array
+     */
+    public function lcsProvider(): array
+    {
+        return [
+            [
+                'nec3ej77p99owvoyd0izmu3blez1wx1e',
+                'hst7pmceigql84smrmql9r5vuwilzpqs',
+                7
+            ],
+            [
+                'zjos9xl7z5zs3g0spms3omzc7vtj5rwo',
+                'ls8f0krkimz419jh',
+                6
+            ],
+            [
+                'ocjxq1za7sa0g6x1',
+                '',
+                0
+            ],
+            [
+                '',
+                'qs0z58kvwgrvtpoy',
+                0
+            ],
+            [
+                'ΛΕΡΒΗΔΟΗΜΑΕΞΞΘΒΗ',
+                'ΗΝΞΛΒΑΚΛ',
+                3
+            ],
+        ];
+    }
+}