├── .github └── workflows │ ├── coveralls.yaml │ └── phpunit.yaml ├── CHANGELOG.md ├── LICENSE.md ├── README.md └── src ├── ConnectedComponent.php ├── Dijkstra.php └── MyersDiff.php /.github/workflows/coveralls.yaml: -------------------------------------------------------------------------------- 1 | name: Coverage 2 | 3 | on: [push, pull_request] 4 | 5 | jobs: 6 | run: 7 | runs-on: ubuntu-latest 8 | 9 | name: coveralls.io 10 | 11 | env: 12 | COVERALLS_REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }} 13 | 14 | steps: 15 | - uses: actions/checkout@v2 16 | - run: composer validate --strict 17 | - run: composer install --no-interaction 18 | - run: XDEBUG_MODE=coverage vendor/bin/phpunit --coverage-clover=build/logs/clover.xml 19 | - run: composer global require php-coveralls/php-coveralls 20 | - run: vendor/bin/php-coveralls --verbose 21 | -------------------------------------------------------------------------------- /.github/workflows/phpunit.yaml: -------------------------------------------------------------------------------- 1 | name: Unit tests 2 | 3 | on: [push, pull_request] 4 | 5 | jobs: 6 | run: 7 | runs-on: ubuntu-latest 8 | 9 | strategy: 10 | matrix: 11 | php-version: ['5.3', '5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0'] 12 | 13 | name: Testing PHP ${{ matrix.php-version }} 14 | 15 | steps: 16 | - uses: shivammathur/setup-php@master 17 | with: 18 | php-version: ${{ matrix.php-version }} 19 | 20 | - uses: actions/checkout@v2 21 | 22 | - run: composer validate --strict 23 | - run: composer install --no-interaction 24 | - run: vendor/bin/phpunit 25 | -------------------------------------------------------------------------------- /CHANGELOG.md: -------------------------------------------------------------------------------- 1 | CHANGE LOG 2 | ========== 3 | 4 | ## 1.6.0 (2021-09-03) 5 | - Allow a user-defined comparison function for Myers-Diff. 6 | - Add PHP 7.4 and 8.0 to the test matrix. 7 | 8 | ## 1.5.1 (2018-12-24) 9 | - Workaround for each() sometimes fails on PHP7.3 10 | 11 | ## 1.5.0 (2018-09-07) 12 | - Fix compatibility with PHP5.3 13 | - Adopt PSR12 code style 14 | 15 | ## 1.4.0 (2017-08-21) 16 | - each() is deprecated in PHP7.2 17 | 18 | ## 1.3.0 (2016-12-05) 19 | - Find the connected components of a graph using a depth-first search. 20 | 21 | ## 1.2.1 (2016-11-08) 22 | - Simplify Myers’ diff by using zero-based array indexes. 23 | 24 | ## 1.2.0 (2016-11-07) 25 | - Fix bug in Myers’ diff. Thanks to Andreas Brunnschweiler for finding the bug and the fix. 26 | - Add PHP7.0 to unit tests. 27 | 28 | ## 1.1.0 (2015-10-20) 29 | - Myers’ diff 30 | 31 | ## 1.0.1 (2015-05-15) 32 | - Exclude test scripts in export. 33 | 34 | ## 1.0.0 (2015-02-15) 35 | - Dijkstra. 36 | -------------------------------------------------------------------------------- /LICENSE.md: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | ========================== 3 | 4 | Version 3, 29 June 2007 5 | 6 | Copyright © 2007 Free Software Foundation, Inc. <> 7 | 8 | Everyone is permitted to copy and distribute verbatim copies 9 | of this license document, but changing it is not allowed. 10 | 11 | ## Preamble 12 | 13 | The GNU General Public License is a free, copyleft license for 14 | software and other kinds of works. 15 | 16 | The licenses for most software and other practical works are designed 17 | to take away your freedom to share and change the works. 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EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 596 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY 597 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 598 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 599 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 600 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 601 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 602 | 603 | ### 16. Limitation of Liability. 604 | 605 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 606 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 607 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 608 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 609 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 610 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 611 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 612 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 613 | SUCH DAMAGES. 614 | 615 | ### 17. Interpretation of Sections 15 and 16. 616 | 617 | If the disclaimer of warranty and limitation of liability provided 618 | above cannot be given local legal effect according to their terms, 619 | reviewing courts shall apply local law that most closely approximates 620 | an absolute waiver of all civil liability in connection with the 621 | Program, unless a warranty or assumption of liability accompanies a 622 | copy of the Program in return for a fee. 623 | 624 | END OF TERMS AND CONDITIONS 625 | 626 | ## How to Apply These Terms to Your New Programs 627 | 628 | If you develop a new program, and you want it to be of the greatest 629 | possible use to the public, the best way to achieve this is to make it 630 | free software which everyone can redistribute and change under these terms. 631 | 632 | To do so, attach the following notices to the program. It is safest 633 | to attach them to the start of each source file to most effectively 634 | state the exclusion of warranty; and each file should have at least 635 | the “copyright” line and a pointer to where the full notice is found. 636 | 637 | 638 | Copyright (C) 639 | 640 | This program is free software: you can redistribute it and/or modify 641 | it under the terms of the GNU General Public License as published by 642 | the Free Software Foundation, either version 3 of the License, or 643 | (at your option) any later version. 644 | 645 | This program is distributed in the hope that it will be useful, 646 | but WITHOUT ANY WARRANTY; without even the implied warranty of 647 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 648 | GNU General Public License for more details. 649 | 650 | You should have received a copy of the GNU General Public License 651 | along with this program. If not, see . 652 | 653 | Also add information on how to contact you by electronic and paper mail. 654 | 655 | If the program does terminal interaction, make it output a short 656 | notice like this when it starts in an interactive mode: 657 | 658 | Copyright (C) 659 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 660 | This is free software, and you are welcome to redistribute it 661 | under certain conditions; type `show c' for details. 662 | 663 | The hypothetical commands `show w' and `show c' should show the appropriate 664 | parts of the General Public License. Of course, your program’s commands 665 | might be different; for a GUI interface, you would use an “about box”. 666 | 667 | You should also get your employer (if you work as a programmer) or school, 668 | if any, to sign a “copyright disclaimer” for the program, if necessary. 669 | For more information on this, and how to apply and follow the GNU GPL, see 670 | <>. 671 | 672 | The GNU General Public License does not permit incorporating your program 673 | into proprietary programs. If your program is a subroutine library, you 674 | may consider it more useful to permit linking proprietary applications with 675 | the library. If this is what you want to do, use the GNU Lesser General 676 | Public License instead of this License. But first, please read 677 | <>. 678 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | [![Latest Stable Version](https://poser.pugx.org/fisharebest/algorithm/v/stable.svg)](https://packagist.org/packages/fisharebest/algorithm) 2 | [![Unit tests](https://github.com/fisharebest/algorithm/actions/workflows/phpunit.yaml/badge.svg)](https://github.com/fisharebest/algorithm/actions/workflows/phpunit.yaml) 3 | [![Coverage Status](https://coveralls.io/repos/fisharebest/algorithm/badge.svg?branch=main)](https://coveralls.io/r/fisharebest/algorithm?branch=main) 4 | [![SensioLabsInsight](https://insight.symfony.com/projects/4997a2c6-fb22-433e-92c5-ae7285f1a5a0/mini.png)](https://insight.symfony.com/projects/4997a2c6-fb22-433e-92c5-ae7285f1a5a0) 5 | [![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/fisharebest/algorithm/badges/quality-score.png?b=main)](https://scrutinizer-ci.com/g/fisharebest/algorithm/?branch=main) 6 | [![StyleCI](https://github.styleci.io/repos/30823747/shield)](https://github.styleci.io/repos/30823747) 7 | [![Code Climate](https://codeclimate.com/github/fisharebest/algorithm/badges/gpa.svg)](https://codeclimate.com/github/fisharebest/algorithm) 8 | 9 | # fisharebest/algorithm 10 | 11 | General purpose algorithms in PHP 12 | 13 | * Dijkstra 14 | * Myers’ diff 15 | * Connected/unconnected components of a graph 16 | 17 | ## Installation 18 | 19 | Install using composer. 20 | 21 | ``` 22 | composer require fisharebest/algorithm 23 | ``` 24 | 25 | 26 | ## Dijkstra 27 | 28 | [Dijkstra's algorithm](https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm) finds the 29 | shortest path(s) between two nodes in a weighted, directed graph. 30 | 31 | Graphs are specified as an array of edges, each with a cost. The example below is 32 | an undirected graph (i.e. if D→E is 9, then E→D is also 9.), because it is easy to 33 | understand and easy to draw. However, the algorithm works equally well for directed 34 | graphs, where links can be one-way only or have different costs in each direction. 35 | ``` 36 | D---9---E 37 | / \ \ 38 | 14 2 6 39 | / \ \ 40 | A---9---B--11--C 41 | \ / / 42 | 7 10 / 43 | \ / / 44 | F-----15 G 45 | ``` 46 | 47 | Sample code for the above graph. 48 | 49 | ``` php 50 | $graph = array( 51 | 'A' => array('B' => 9, 'D' => 14, 'F' => 7), 52 | 'B' => array('A' => 9, 'C' => 11, 'D' => 2, 'F' => 10), 53 | 'C' => array('B' => 11, 'E' => 6, 'F' => 15), 54 | 'D' => array('A' => 14, 'B' => 2, 'E' => 9), 55 | 'E' => array('C' => 6, 'D' => 9), 56 | 'F' => array('A' => 7, 'B' => 10, 'C' => 15), 57 | 'G' => array(), 58 | ); 59 | 60 | $algorithm = new \Fisharebest\Algorithm\Dijkstra($graph); 61 | 62 | // There can be zero, one or more shortest (i.e. same total cost) paths. 63 | 64 | // No shortest path. 65 | $path = $algorithm->shortestPaths('A', 'G'); // array() 66 | 67 | // Exactly one shortest path. 68 | $path = $algorithm->shortestPaths('A', 'E'); // array(array('A', 'B', 'D', 'E')) 69 | 70 | // Multiple solutions with the same shortest path. 71 | $path = $algorithm->shortestPaths('E', 'F'); // array(array('E', 'D', 'B', 'F'), array('E', 'C', 'F')) 72 | 73 | // To find next-shortest paths, exclude one or more intermediate nodes from the shortest path. 74 | $path = $algorithm->shortestPaths('A', 'E'); // array(array('A', 'B', 'D', 'E')) 75 | $path = $algorithm->shortestPaths('A', 'E', array('B')); // array(array('A', 'B', 'D', 'E')) 76 | $path = $algorithm->shortestPaths('A', 'E', array('D')); // array(array('A', 'B', 'C', 'E')) 77 | $path = $algorithm->shortestPaths('A', 'E', array('B', 'D')); // array(array('A', 'F', 'C', 'E')) 78 | ``` 79 | 80 | ## Myers’ diff 81 | 82 | Find the difference between two sequences of tokens (characters, words, lines, etc.) using 83 | “[An O(ND) Difference Algorithm and Its Variations](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.4.6927)” 84 | by Eugene W. Myers. 85 | 86 | The output can be interpreted as either: 87 | 88 | * A series of instructions to transform the first sequence into the second sequence. 89 | * A list of matches (tokens that appear in both sequences) and mismatches (tokens that appear in 90 | just one sequence). 91 | 92 | ``` php 93 | $x = array('a', 'b', 'c', 'a', 'b', 'b', 'a'); 94 | $y = array('c', 'b', 'a', 'b', 'a', 'c'); 95 | $algorithm = new MyersDiff; 96 | $diff = $algorithm->calculate($x, $y); 97 | // array( 98 | // array('a', MyersDiff::DELETE), i.e. 'a' occurs only in $x 99 | // array('b', MyersDiff::DELETE), i.e. 'b' occurs only in $x 100 | // array('c', MyersDiff::KEEP), i.e. 'c' occurs both $x and $y 101 | // array('b', MyersDiff::INSERT), i.e. 'b' occurs only in $y 102 | // array('a', MyersDiff::KEEP), i.e. 'a' occurs in both $x and $y 103 | // array('b', MyersDiff::KEEP), i.e. 'b' occurs in both $x and $y 104 | // array('b', MyersDiff::DELETE), i.e. 'b' occurs only in $x 105 | // array('a', MyersDiff::KEEP), i.e. 'a' occurs in both $x and $y 106 | // array('c', MyersDiff::INSERT), i.e. 'c' occurs only in $y 107 | // ); 108 | ``` 109 | ## Connected components 110 | 111 | A depth-first search of a graph to find isolated groups of nodes. 112 | 113 | ``` 114 | D E 115 | / \ \ 116 | / \ \ 117 | A-----B C 118 | \ / 119 | \ / 120 | F 121 | ``` 122 | 123 | Sample code for the above graph 124 | 125 | ```php 126 | $graph = array( 127 | 'A' => array('B' => 1, 'D' => 1, 'F' => 1), 128 | 'B' => array('A' => 1, 'D' => 1, 'F' => 1), 129 | 'C' => array('E' => 1), 130 | 'D' => array('A' => 1, 'B' => 1), 131 | 'E' => array('C' => 1), 132 | 'F' => array('A' => 1, 'B' => 1), 133 | ); 134 | 135 | $algorithm = new \Fisharebest\Algorithm\ConnectedComponent($graph); 136 | $components = $algorithm->findConnectedComponents()); 137 | // array( 138 | // 1 => array('A', 'B', 'D', 'F'), 139 | // 2 => array('C', 'E'), 140 | // ); 141 | ``` 142 | -------------------------------------------------------------------------------- /src/ConnectedComponent.php: -------------------------------------------------------------------------------- 1 | 7 | * @copyright (c) 2021 Greg Roach 8 | * @license GPL-3.0+ 9 | * 10 | * This program is free software: you can redistribute it and/or modify 11 | * it under the terms of the GNU General Public License as published by 12 | * the Free Software Foundation, either version 3 of the License, or 13 | * (at your option) any later version. 14 | * This program is distributed in the hope that it will be useful, 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 | * GNU General Public License for more details. 18 | * You should have received a copy of the GNU General Public License 19 | * along with this program. If not, see . 20 | */ 21 | 22 | /** 23 | * Class ConnectedComponent - Use a depth-first search to find connected 24 | * components of an undirected graph. 25 | */ 26 | class ConnectedComponent 27 | { 28 | /** @var integer[][] The graph, where $graph[node1][node2]=cost */ 29 | protected $graph; 30 | 31 | /** @var int[] The component number for each node */ 32 | protected $nodes; 33 | 34 | /** @var int The next connected-component to find. */ 35 | protected $component; 36 | 37 | /** 38 | * @param integer[][] $graph 39 | */ 40 | public function __construct($graph) 41 | { 42 | $this->graph = $graph; 43 | $this->nodes = array_fill_keys(array_keys($graph), 0); 44 | $this->component = 0; 45 | } 46 | 47 | /** 48 | * An array of components (arrays). 49 | * 50 | * @return array 51 | */ 52 | public function findConnectedComponents() 53 | { 54 | // Find the first unallocated node 55 | $node = array_search(0, $this->nodes, true); 56 | 57 | while ($node !== false) { 58 | // Find the next connected-component. 59 | $this->component++; 60 | $this->depthFirstSearch($node, $this->component); 61 | 62 | // Find the next unallocated node. 63 | $node = array_search(0, $this->nodes, true); 64 | } 65 | 66 | return $this->groupResults(); 67 | } 68 | 69 | /** 70 | * Group the nodes by component. 71 | * 72 | * @return array 73 | */ 74 | private function groupResults() 75 | { 76 | $result = array(); 77 | foreach ($this->nodes as $node => $component) { 78 | if (array_key_exists($component, $result)) { 79 | $result[$component][] = $node; 80 | } else { 81 | $result[$component] = array($node); 82 | } 83 | } 84 | 85 | return $result; 86 | } 87 | 88 | /** 89 | * Find all nodes connected to $node and mark them as part of 90 | * component $component. 91 | * 92 | * @param $node 93 | * @param $component 94 | */ 95 | private function depthFirstSearch($node, $component) 96 | { 97 | $this->nodes[$node] = $component; 98 | 99 | foreach (array_keys($this->graph[$node]) as $next) { 100 | if ($this->nodes[$next] === 0) { 101 | $this->depthFirstSearch($next, $component); 102 | } 103 | } 104 | } 105 | } 106 | -------------------------------------------------------------------------------- /src/Dijkstra.php: -------------------------------------------------------------------------------- 1 | 7 | * @copyright (c) 2021 Greg Roach 8 | * @license GPL-3.0+ 9 | * 10 | * This program is free software: you can redistribute it and/or modify 11 | * it under the terms of the GNU General Public License as published by 12 | * the Free Software Foundation, either version 3 of the License, or 13 | * (at your option) any later version. 14 | * This program is distributed in the hope that it will be useful, 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 | * GNU General Public License for more details. 18 | * You should have received a copy of the GNU General Public License 19 | * along with this program. If not, see . 20 | */ 21 | 22 | /** 23 | * Class Dijkstra - Use Dijkstra's algorithm to calculate the shortest path 24 | * through a weighted, directed graph. 25 | */ 26 | class Dijkstra 27 | { 28 | /** @var integer[][] The graph, where $graph[node1][node2]=cost */ 29 | protected $graph; 30 | 31 | /** @var int[] Distances from the source node to each other node */ 32 | protected $distance; 33 | 34 | /** @var string[][] The previous node(s) in the path to the current node */ 35 | protected $previous; 36 | 37 | /** @var int[] Nodes which have yet to be processed */ 38 | protected $queue; 39 | 40 | /** 41 | * @param integer[][] $graph 42 | */ 43 | public function __construct($graph) 44 | { 45 | $this->graph = $graph; 46 | } 47 | 48 | /** 49 | * Process the next (i.e. closest) entry in the queue. 50 | * 51 | * @param string[] $exclude A list of nodes to exclude - for calculating next-shortest paths. 52 | * 53 | * @return void 54 | */ 55 | protected function processNextNodeInQueue(array $exclude) 56 | { 57 | // Process the closest vertex 58 | $closest = array_search(min($this->queue), $this->queue); 59 | if (!empty($this->graph[$closest]) && !in_array($closest, $exclude)) { 60 | foreach ($this->graph[$closest] as $neighbor => $cost) { 61 | if (isset($this->distance[$neighbor])) { 62 | if ($this->distance[$closest] + $cost < $this->distance[$neighbor]) { 63 | // A shorter path was found 64 | $this->distance[$neighbor] = $this->distance[$closest] + $cost; 65 | $this->previous[$neighbor] = array($closest); 66 | $this->queue[$neighbor] = $this->distance[$neighbor]; 67 | } elseif ($this->distance[$closest] + $cost === $this->distance[$neighbor]) { 68 | // An equally short path was found 69 | $this->previous[$neighbor][] = $closest; 70 | $this->queue[$neighbor] = $this->distance[$neighbor]; 71 | } 72 | } 73 | } 74 | } 75 | unset($this->queue[$closest]); 76 | } 77 | 78 | /** 79 | * Extract all the paths from $source to $target as arrays of nodes. 80 | * 81 | * @param string $target The starting node (working backwards) 82 | * 83 | * @return string[][] One or more shortest paths, each represented by a list of nodes 84 | */ 85 | protected function extractPaths($target) 86 | { 87 | $paths = array(array($target)); 88 | 89 | for ($key = 0; isset($paths[$key]); ++$key) { 90 | $path = $paths[$key]; 91 | 92 | if (!empty($this->previous[$path[0]])) { 93 | foreach ($this->previous[$path[0]] as $previous) { 94 | $copy = $path; 95 | array_unshift($copy, $previous); 96 | $paths[] = $copy; 97 | } 98 | unset($paths[$key]); 99 | } 100 | } 101 | 102 | return array_values($paths); 103 | } 104 | 105 | /** 106 | * Calculate the shortest path through a a graph, from $source to $target. 107 | * 108 | * @param string $source The starting node 109 | * @param string $target The ending node 110 | * @param string[] $exclude A list of nodes to exclude - for calculating next-shortest paths. 111 | * 112 | * @return string[][] Zero or more shortest paths, each represented by a list of nodes 113 | */ 114 | public function shortestPaths($source, $target, array $exclude = array()) 115 | { 116 | // The shortest distance to all nodes starts with infinity... 117 | $this->distance = array_fill_keys(array_keys($this->graph), INF); 118 | // ...except the start node 119 | $this->distance[$source] = 0; 120 | 121 | // The previously visited nodes 122 | $this->previous = array_fill_keys(array_keys($this->graph), array()); 123 | 124 | // Process all nodes in order 125 | $this->queue = array($source => 0); 126 | while (!empty($this->queue)) { 127 | $this->processNextNodeInQueue($exclude); 128 | } 129 | 130 | if ($source === $target) { 131 | // A null path 132 | return array(array($source)); 133 | } elseif (empty($this->previous[$target])) { 134 | // No path between $source and $target 135 | return array(); 136 | } else { 137 | // One or more paths were found between $source and $target 138 | return $this->extractPaths($target); 139 | } 140 | } 141 | } 142 | -------------------------------------------------------------------------------- /src/MyersDiff.php: -------------------------------------------------------------------------------- 1 | 7 | * @copyright (c) 2021 Greg Roach 8 | * @license GPL-3.0+ 9 | * 10 | * This program is free software: you can redistribute it and/or modify 11 | * it under the terms of the GNU General Public License as published by 12 | * the Free Software Foundation, either version 3 of the License, or 13 | * (at your option) any later version. 14 | * This program is distributed in the hope that it will be useful, 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 | * GNU General Public License for more details. 18 | * You should have received a copy of the GNU General Public License 19 | * along with this program. If not, see . 20 | */ 21 | 22 | /** 23 | * Class MyersDiff - find the shortest edit sequence to transform one string into another. 24 | * 25 | * Based on "An O(ND) Difference Algorithm and Its Variations" by Eugene W Myers. 26 | * 27 | * http://www.xmailserver.org/diff2.pdf 28 | * http://www.codeproject.com/Articles/42279/Investigating-Myers-diff-algorithm-Part-of 29 | */ 30 | class MyersDiff 31 | { 32 | /** Instruction to delete a token which only appears in the first sequence */ 33 | const DELETE = -1; 34 | 35 | /** Instruction to keep a token which is common to both sequences */ 36 | const KEEP = 0; 37 | 38 | /** Instruction to insert a token which only appears in the last sequence */ 39 | const INSERT = 1; 40 | 41 | /** 42 | * Backtrack through the intermediate results to extract the "snakes" that 43 | * are visited on the chosen "D-path". 44 | * 45 | * @param string[] $v_save Intermediate results 46 | * @param int $x End position 47 | * @param int $y End position 48 | * 49 | * @return list 50 | */ 51 | private function extractSnakes(array $v_save, $x, $y) 52 | { 53 | $snakes = array(); 54 | for ($d = count($v_save) - 1; $x >= 0 && $y >= 0; $d--) { 55 | array_unshift($snakes, array($x, $y)); 56 | 57 | $v = $v_save[$d]; 58 | $k = $x - $y; 59 | 60 | if ($k === -$d || $k !== $d && $v[$k - 1] < $v[$k + 1]) { 61 | $k_prev = $k + 1; 62 | } else { 63 | $k_prev = $k - 1; 64 | } 65 | 66 | $x = $v[$k_prev]; 67 | $y = $x - $k_prev; 68 | } 69 | 70 | return $snakes; 71 | } 72 | 73 | /** 74 | * Convert a list of "snakes" into a set of insert/keep/delete instructions. 75 | * 76 | * @template T 77 | * 78 | * @param list $snakes Common subsequences 79 | * @param list $a First sequence 80 | * @param list $b Second sequence 81 | * 82 | * @return list - pairs of token and edit (-1 for delete, 0 for keep, +1 for insert) 83 | */ 84 | private function formatSolution(array $snakes, array $a, array $b) 85 | { 86 | $solution = array(); 87 | $x = 0; 88 | $y = 0; 89 | foreach ($snakes as $snake) { 90 | // Horizontals 91 | while ($snake[0] - $snake[1] > $x - $y) { 92 | $solution[] = array($a[$x], self::DELETE); 93 | $x++; 94 | } 95 | // Verticals 96 | while ($snake[0] - $snake[1] < $x - $y) { 97 | $solution[] = array($b[$y], self::INSERT); 98 | $y++; 99 | } 100 | // Diagonals 101 | while ($x < $snake[0]) { 102 | $solution[] = array($a[$x], self::KEEP); 103 | $x++; 104 | $y++; 105 | } 106 | } 107 | 108 | return $solution; 109 | } 110 | 111 | /** 112 | * Calculate the shortest edit sequence to convert $x into $y. 113 | * 114 | * @template T 115 | * 116 | * @param list $a - List of values to compare. 117 | * @param list $b - List of values to compare. 118 | * @param (callable(T, T): bool)|null $compare - comparison function for tokens, or NULL to use === comparison. 119 | * 120 | * @return list - pairs of token and edit (-1 for delete, 0 for keep, +1 for insert) 121 | */ 122 | public function calculate(array $a, array $b, $compare = null) 123 | { 124 | if ($compare === null) { 125 | $compare = function ($x, $y) { 126 | return $x === $y; 127 | }; 128 | } 129 | 130 | // The algorithm uses array keys numbered from zero. 131 | $n = count($a); 132 | $m = count($b); 133 | $a = array_values($a); 134 | $b = array_values($b); 135 | $max = $m + $n; 136 | 137 | // Keep a copy of $v after each iteration of $d. 138 | $v_save = array(); 139 | 140 | // Find the shortest "D-path". 141 | $v = array(1 => 0); 142 | for ($d = 0; $d <= $max; $d++) { 143 | // Examine all possible "K-lines" for this "D-path". 144 | for ($k = -$d; $k <= $d; $k += 2) { 145 | if ($k === -$d || $k !== $d && $v[$k - 1] < $v[$k + 1]) { 146 | // Move down. 147 | $x = $v[$k + 1]; 148 | } else { 149 | // Move right. 150 | $x = $v[$k - 1] + 1; 151 | } 152 | // Derive Y from X. 153 | $y = $x - $k; 154 | // Follow the diagonal. 155 | while ($x < $n && $y < $m && $compare($a[$x], $b[$y])) { 156 | $x++; 157 | $y++; 158 | } 159 | // Just store X, as we can calculate Y (from X + K). 160 | $v[$k] = $x; 161 | $v_save[$d] = $v; 162 | // Solution found? 163 | if ($x === $n && $y === $m) { 164 | break 2; 165 | } 166 | } 167 | } 168 | 169 | // Extract the solution by back-tracking through the saved results. 170 | $snakes = $this->extractSnakes($v_save, $n, $m); 171 | 172 | // Format the snakes as a set of instructions. 173 | return $this->formatSolution($snakes, $a, $b); 174 | } 175 | } 176 | --------------------------------------------------------------------------------