LCS::findMiddleSnake() - Code Metrics - snebes/php-daisydiff - Measure and Improve Code Quality continuously with Scrutinizer

LCS::findMiddleSnake() F
last analyzed 2019-09-10 16:50 UTC

↳ Parent: LCS

Complexity

Conditions	33
Paths	1808

Size

Total Lines	119
Code Lines	67

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	61
CRAP Score	33.4742

Importance

Changes

Metric	Value
cc	33
eloc	67
nc	1808
nop	6
dl	0
loc	119
ccs	61
cts	66
cp	0.9242
crap	33.4742
rs	0
c	0
b	0
f	0

How to fix Long Method Complexity

<?php
/**
 * (c) Steve Nebes <[email protected]>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

declare(strict_types=1);

namespace SN\DaisyDiff\RangeDifferencer\Core;

/**
 * LCS - Longest Common Subsequence - Common Methods.
 *
 * Used to determine the change set responsible for each line.
 */
abstract class LCS
{
    /** @var int */
    private $maxDifferences = 0;

    /** @var int */
    private $length = 0;

    /**
     * @return int
     */
    public function getLength(): int
    {
        return $this->length;
    }

    /**
     * Myers' algorithm for longest common subsequence. O((M + N)D) worst case time, O(M + N + D^2) expected time,
     * O(M + N) space (http://citeseer.ist.psu.edu/myers86ond.html)
     *
     * Note: Beyond implementing the algorithm as described in the paper I have added diagonal range compression which
     * helps when finding the LCS of a very long and a very short sequence, also bound the running time to (N + M)^1.5
     * when both sequences are very long.
     *
     * After this method is called, the longest common subsequence is available by calling getResult() where result[0]
     * is composed of entries from l1 and result[1] is composed of entries from l2
     *
     * @param LCSSettings $settings
     * @return void
     */
    public function longestCommonSubsequence(LCSSettings $settings): void
    {
        $length1 = $this->getLength1();
        $length2 = $this->getLength2();

        if (0 === $length1 || 0 === $length2) {
            $this->length = 0;

            return;
        }

        $this->maxDifferences = (int) (($length1 + $length2 + 1) / 2);

        if ((float) $length1 * (float) $length2 > $settings->getTooLong()) {
            // Limit complexity to D^POW_LIMIT for long sequences
            $this->maxDifferences = (int) (\pow($this->maxDifferences, $settings->getPowLimit() - 1.0));
        }

        $this->initializeLcs($length1);

        // The common prefixes and suffixes are always part of some LCS, include them now to reduce our search space.
        $max = \min($length1, $length2);

        for (
            $forwardBound = 0;
            $forwardBound < $max && $this->isRangeEqual($forwardBound, $forwardBound);
            $forwardBound++
        ) {
            $this->setLcs($forwardBound, $forwardBound);
        }

        $backBoundL1 = $length1 - 1;
        $backBoundL2 = $length2 - 1;

        while ($backBoundL1 >= $forwardBound &&
            $backBoundL2 >= $forwardBound &&
            $this->isRangeEqual($backBoundL1, $backBoundL2)) {
            $this->setLcs($backBoundL1, $backBoundL2);
            $backBoundL1--;
            $backBoundL2--;
        }

        $V = \array_fill(0, 2, \array_fill(0, $length1 + $length2 + 1, 0));
        $snake = [0, 0, 0];
        $lcsRec = $this->lcsRec($forwardBound, $backBoundL1, $forwardBound, $backBoundL2, $V, $snake);

        $this->length = $forwardBound + $length1 - $backBoundL1 - 1 + $lcsRec;
    }

    /**
     * The recursive helper function for Myers' LCS. Computes the LCS of l1[bottoml1 .. topl1] and l2[bottoml2 .. topl2]
     * fills in the appropriate location in lcs and returns the length.
     *
     * @param int     $bottomL1
     * @param int     $topL1
     * @param int     $bottomL2
     * @param int     $topL2
     * @param int[][] $V
     * @param int[]   $snake
     * @return int
     */
    private function lcsRec(int $bottomL1, int $topL1, int $bottomL2, int $topL2, array &$V, array &$snake): int
    {
        // Check that both sequences are non-empty.
        if ($bottomL1 > $topL1 || $bottomL2 > $topL2) {
            return 0;
        }

        /** @var int */
        $d = $this->findMiddleSnake($bottomL1, $topL1, $bottomL2, $topL2, $V, $snake);

        // Need to store these so we don't lose them when they're overwritten by the recursion.
        $len = $snake[2];
        $startX = $snake[0];
        $startY = $snake[1];

        // The middle snake is part of the LCS, store it.
        for ($i = 0; $i < $len; $i++) {
            $this->setLcs($startX + $i, $startY + $i);
        }

        if ($d > 1) {
            $lcs1 = $this->lcsRec($bottomL1, $startX - 1, $bottomL2, $startY - 1, $V, $snake);
            $lcs2 = $this->lcsRec($startX + $len, $topL1, $startY + $len, $topL2, $V, $snake);

            return (int) ($len + $lcs1 + $lcs2);
        } elseif ($d === 1) {
            // In this case the sequences differ by exactly 1 line. We have already saved all the lines after the
            // difference in the for loop above, now we need to save all the lines before the difference.
            $max = \min($startX - $bottomL1, $startY - $bottomL2);

            for ($i = 0; $i < $max; $i++) {
                $this->setLcs($bottomL1 + $i, $bottomL2 + $i);
            }

            return $max + $len;
        }

        return $len;
    }

    /**
     * Helper function for Myers' LCS algorithm to find the middle snake for l1[bottoml1..topl1] and l2[bottoml2..topl2]
     * The x, y coodrdinates of the start of the middle snake are saved in snake[0], snake[1] respectively and the
     * length of the snake is saved in s[2].
     *
     * @param int     $bottomL1
     * @param int     $topL1
     * @param int     $bottomL2
     * @param int     $topL2
     * @param int[][] $V
     * @param int[]   $snake
     * @return int
     */
    private function findMiddleSnake(
        int $bottomL1,
        int $topL1,
        int $bottomL2,
        int $topL2,
        array &$V,
        array &$snake
    ): int {
        $N = $topL1 - $bottomL1 + 1;
        $M = $topL2 - $bottomL2 + 1;

        $delta = $N - $M;
        $isEven = ($delta & 1) === 1 ? false : true;

        $limit = \min($this->maxDifferences, (int) (($N + $M + 1) / 2));

        // Offset to make it odd/even.
        // a 0 or 1 that we add to the start offset to make it odd/even
        $valueToAddForward = ($M & 1) === 1 ? 1 : 0;
        $valueToAddBackward = ($N & 1) === 1 ? 1 : 0;

        $startForward = -$M;
        $endForward = $N;
        $startBackward = -$N;
        $endBackward = $M;

        $V[0][$limit + 1] = 0;
        $V[1][$limit - 1] = $N;

        for ($d = 0; $d <= $limit; $d++) {
            $startDiag = \max($valueToAddForward + $startForward, -$d);
            $endDiag = \min($endForward, $d);
            $valueToAddForward = 1 - $valueToAddForward;

            // Compute forward furthest reaching paths.
            for ($k = $startDiag; $k <= $endDiag; $k += 2) {
                if ($k === -$d || ($k < $d && $V[0][$limit + $k - 1] < $V[0][$limit + $k + 1])) {
                    $x = $V[0][$limit + $k + 1];
                } else {
                    $x = $V[0][$limit + $k - 1] + 1;
                }

                $y = $x - $k;

                $snake[0] = $x + $bottomL1;
                $snake[1] = $y + $bottomL2;
                $snake[2] = 0;

                while ($x < $N && $y < $M && $this->isRangeEqual($x + $bottomL1, $y + $bottomL2)) {
                    $x++;
                    $y++;
                    $snake[2]++;
                }

                $V[0][$limit + $k] = $x;

                if (!$isEven && $k >= $delta - $d + 1 && $k <= $delta + $d - 1 && $x >= $V[1][$limit + $k - $delta]) {
                    return (int) (2 * $d - 1);
                }

                // Check to see if we can cut down the diagonal range.
                if ($x >= $N && $endForward > $k - 1) {
                    $endForward = $k - 1;
                } elseif ($y >= $M) {
                    $startForward = $k + 1;
                    $valueToAddForward = 0;
                }
            }

            $startDiag = \max($valueToAddBackward + $startBackward, -$d);
            $endDiag = \min($endBackward, $d);
            $valueToAddBackward = 1 - $valueToAddBackward;

            // Compute backward furthest reaching paths.
            for ($k = $startDiag; $k <= $endDiag; $k += 2) {
                if ($k === $d || ($k !== -$d && $V[1][$limit + $k - 1] < $V[1][$limit + $k + 1])) {
                    $x = $V[1][$limit + $k - 1];
                } else {
                    $x = $V[1][$limit + $k + 1] - 1;
                }

                $y = $x - $k - $delta;
                $snake[2] = 0;

                while ($x > 0 && $y > 0 && $this->isRangeEqual($x - 1 + $bottomL1, $y - 1 + $bottomL2)) {
                    $x--;
                    $y--;
                    $snake[2]++;
                }

                $V[1][$limit + $k] = $x;

                if ($isEven && $k >= -$delta - $d && $k <= $d - $delta && $x <= $V[0][$limit + $k + $delta]) {
                    $snake[0] = $bottomL1 + $x;
                    $snake[1] = $bottomL2 + $y;

                    return (int) (2 * $d);
                }

                // Check to see if we can cut down our diagonal range.
                if ($x <= 0) {
                    $startBackward = $k + 1;
                    $valueToAddBackward = 0;
                } elseif ($y <= 0 && $endBackward > $k - 1) {
                    $endBackward = $k - 1;
                }
            }
        }

        // Computing the true LCS is too expensive, instead find the diagonal with the most progress and pretend a
        // middle snake of length 0 occurs there.
        /** @var int[] */
        $mostProgress = $this->findMostProgress($M, $N, $limit, $V);

        $snake[0] = $bottomL1 + $mostProgress[0];
        $snake[1] = $bottomL2 + $mostProgress[1];
        $snake[2] = 0;

        return 5;

        // HACK: since we didn't really finish the LCS computation we don't really know the length of the SES. We don't
        // do anything with the result anyway, unless it's <=1. We know for a fact SES > 1 so 5 is as good a number as
        // any to return here.
    }

    /**
     * @param int     $M
     * @param int     $N
     * @param int     $limit
     * @param int[][] $V
     * @return int[]
     */
    private function findMostProgress(int $M, int $N, int $limit, array &$V): array
    {
        $delta = $N - $M;

        if (($M & 1) === ($limit & 1)) {
            $forwardStartDiag = \max(-$M, -$limit);
        } else {
            $forwardStartDiag = \max(1 - $M, -$limit);
        }

        $forwardEndDiag = \min($N, $limit);

        if (($N & 1) === ($limit & 1)) {
            $backwardStartDiag = \max(-$N, -$limit);
        } else {
            $backwardStartDiag = \max(1 - $N, -$limit);
        }

        $backwardEndDiag = \min($M, $limit);
        $maxProgress = \array_fill(0,
            (int) (\max($forwardEndDiag - $forwardStartDiag, $backwardEndDiag - $backwardStartDiag) / 2 + 1),
            [0, 0, 0]);
        $numProgress = 0;
        // the 1st entry is current, it is initialized with 0s.

        // First search the forward diagonals.
        for ($k = $forwardStartDiag; $k <= $forwardEndDiag; $k += 2) {
            $x = $V[0][$limit + $k];
            $y = $x - $k;

            if ($x > $N || $y > $M) {
                continue;
            }

            $progress = $x + $y;

            if ($progress > $maxProgress[0][2]) {
                $numProgress = 0;
                $maxProgress[0][0] = $x;
                $maxProgress[0][1] = $y;
                $maxProgress[0][2] = $progress;
            } elseif ($progress === $maxProgress[0][2]) {
                $numProgress++;
                $maxProgress[$numProgress][0] = $x;
                $maxProgress[$numProgress][1] = $y;
                $maxProgress[$numProgress][2] = $progress;
            }
        }

        // Progress is in the forward direction.
        $maxProgressForward = true;

        // Now search the backward diagonals.
        for ($k = $backwardStartDiag; $k <= $backwardEndDiag; $k += 2) {
            $x = $V[1][$limit + $k];
            $y = $x - $k - $delta;

            if ($x < 0 || $y < 0) {
                continue;
            }

            $progress = $N - $x + $M - $y;

            if ($progress > $maxProgress[0][2]) {
                $numProgress = 0;
                $maxProgressForward = false;
                $maxProgress[0][0] = $x;
                $maxProgress[0][1] = $y;
                $maxProgress[0][2] = $progress;
            } elseif ($progress === $maxProgress[0][2] && !$maxProgressForward) {
                $numProgress++;
                $maxProgress[$numProgress][0] = $x;
                $maxProgress[$numProgress][1] = $y;
                $maxProgress[$numProgress][2] = $progress;
            }
        }

        // Return the middle diagonal with maximum progress.
        return $maxProgress[(int) ($numProgress / 2)];
    }

    /**
     * @return int
     */
    abstract protected function getLength1(): int;

    /**
     * @return int
     */
    abstract protected function getLength2(): int;

    /**
     * @param int $i1
     * @param int $i2
     * @return bool
     */
    abstract protected function isRangeEqual(int $i1, int $i2): bool;

    /**
     * @param int $sl1
     * @param int $sl2
     * @return void
     */
    abstract protected function setLcs(int $sl1, int $sl2): void;

    /**
     * @param int $lcsLength
     * @return void
     */
    abstract protected function initializeLcs(int $lcsLength): void;
}


1		<?php
2		/**
3		* (c) Steve Nebes <[email protected]>
4		*
5		* For the full copyright and license information, please view the LICENSE
6		* file that was distributed with this source code.
7		*/
8
9		declare(strict_types=1);
10
11		namespace SN\DaisyDiff\RangeDifferencer\Core;
12
13		/**
14		* LCS - Longest Common Subsequence - Common Methods.
15		*
16		* Used to determine the change set responsible for each line.
17		*/
18		abstract class LCS
19		{
20		/** @var int */
21		private $maxDifferences = 0;
22
23		/** @var int */
24		private $length = 0;
25
26		/**
27		* @return int
28		*/
29	18	public function getLength(): int
30		{
31	18	return $this->length;
32		}
33
34		/**
35		* Myers' algorithm for longest common subsequence. O((M + N)D) worst case time, O(M + N + D^2) expected time,
36		* O(M + N) space (http://citeseer.ist.psu.edu/myers86ond.html)
37		*
38		* Note: Beyond implementing the algorithm as described in the paper I have added diagonal range compression which
39		* helps when finding the LCS of a very long and a very short sequence, also bound the running time to (N + M)^1.5
40		* when both sequences are very long.
41		*
42		* After this method is called, the longest common subsequence is available by calling getResult() where result[0]
43		* is composed of entries from l1 and result[1] is composed of entries from l2
44		*
45		* @param LCSSettings $settings
46		* @return void
47		*/
48	11	public function longestCommonSubsequence(LCSSettings $settings): void
49		{
50	11	$length1 = $this->getLength1();
51	11	$length2 = $this->getLength2();
52
53	11	if (0 === $length1 \|\| 0 === $length2) {
54		$this->length = 0;
55
56		return;
57		}
58
59	11	$this->maxDifferences = (int) (($length1 + $length2 + 1) / 2);
60
61	11	if ((float) $length1 * (float) $length2 > $settings->getTooLong()) {
62		// Limit complexity to D^POW_LIMIT for long sequences
63		$this->maxDifferences = (int) (\pow($this->maxDifferences, $settings->getPowLimit() - 1.0));
64		}
65
66	11	$this->initializeLcs($length1);
67
68		// The common prefixes and suffixes are always part of some LCS, include them now to reduce our search space.
69	11	$max = \min($length1, $length2);
70
71		for (
72	11	$forwardBound = 0;
73	11	$forwardBound < $max && $this->isRangeEqual($forwardBound, $forwardBound);
74		$forwardBound++
75		) {
76	9	$this->setLcs($forwardBound, $forwardBound);
77		}
78
79	11	$backBoundL1 = $length1 - 1;
80	11	$backBoundL2 = $length2 - 1;
81
82	11	while ($backBoundL1 >= $forwardBound &&
83	11	$backBoundL2 >= $forwardBound &&
84	11	$this->isRangeEqual($backBoundL1, $backBoundL2)) {
85	9	$this->setLcs($backBoundL1, $backBoundL2);
86	9	$backBoundL1--;
87	9	$backBoundL2--;
88		}
89
90	11	$V = \array_fill(0, 2, \array_fill(0, $length1 + $length2 + 1, 0));
91	11	$snake = [0, 0, 0];
92	11	$lcsRec = $this->lcsRec($forwardBound, $backBoundL1, $forwardBound, $backBoundL2, $V, $snake);
93
94	11	$this->length = $forwardBound + $length1 - $backBoundL1 - 1 + $lcsRec;
95	11	}
96
97		/**
98		* The recursive helper function for Myers' LCS. Computes the LCS of l1[bottoml1 .. topl1] and l2[bottoml2 .. topl2]
99		* fills in the appropriate location in lcs and returns the length.
100		*
101		* @param int $bottomL1
102		* @param int $topL1
103		* @param int $bottomL2
104		* @param int $topL2
105		* @param int[][] $V
106		* @param int[] $snake
107		* @return int
108		*/
109	11	private function lcsRec(int $bottomL1, int $topL1, int $bottomL2, int $topL2, array &$V, array &$snake): int
110		{
111		// Check that both sequences are non-empty.
112	11	if ($bottomL1 > $topL1 \|\| $bottomL2 > $topL2) {
113	11	return 0;
114		}
115
116		/** @var int */
117	7	$d = $this->findMiddleSnake($bottomL1, $topL1, $bottomL2, $topL2, $V, $snake);
118
119		// Need to store these so we don't lose them when they're overwritten by the recursion.
120	7	$len = $snake[2];
121	7	$startX = $snake[0];
122	7	$startY = $snake[1];
123
124		// The middle snake is part of the LCS, store it.
125	7	for ($i = 0; $i < $len; $i++) {
126	7	$this->setLcs($startX + $i, $startY + $i);
127		}
128
129	7	if ($d > 1) {
130	7	$lcs1 = $this->lcsRec($bottomL1, $startX - 1, $bottomL2, $startY - 1, $V, $snake);
131	7	$lcs2 = $this->lcsRec($startX + $len, $topL1, $startY + $len, $topL2, $V, $snake);
132
133	7	return (int) ($len + $lcs1 + $lcs2);
134		} elseif ($d === 1) {
135		// In this case the sequences differ by exactly 1 line. We have already saved all the lines after the
136		// difference in the for loop above, now we need to save all the lines before the difference.
137		$max = \min($startX - $bottomL1, $startY - $bottomL2);
138
139		for ($i = 0; $i < $max; $i++) {
140		$this->setLcs($bottomL1 + $i, $bottomL2 + $i);
141		}
142
143		return $max + $len;
144		}
145
146		return $len;
147		}
148
149		/**
150		* Helper function for Myers' LCS algorithm to find the middle snake for l1[bottoml1..topl1] and l2[bottoml2..topl2]
151		* The x, y coodrdinates of the start of the middle snake are saved in snake[0], snake[1] respectively and the
152		* length of the snake is saved in s[2].
153		*
154		* @param int $bottomL1
155		* @param int $topL1
156		* @param int $bottomL2
157		* @param int $topL2
158		* @param int[][] $V
159		* @param int[] $snake
160		* @return int
161		*/
162	7	private function findMiddleSnake(
163		int $bottomL1,
164		int $topL1,
165		int $bottomL2,
166		int $topL2,
167		array &$V,
168		array &$snake
169		): int {
170	7	$N = $topL1 - $bottomL1 + 1;
171	7	$M = $topL2 - $bottomL2 + 1;
172
173	7	$delta = $N - $M;
174	7	$isEven = ($delta & 1) === 1 ? false : true;
175
176	7	$limit = \min($this->maxDifferences, (int) (($N + $M + 1) / 2));
177
178		// Offset to make it odd/even.
179		// a 0 or 1 that we add to the start offset to make it odd/even
180	7	$valueToAddForward = ($M & 1) === 1 ? 1 : 0;
181	7	$valueToAddBackward = ($N & 1) === 1 ? 1 : 0;
182
183	7	$startForward = -$M;
184	7	$endForward = $N;
185	7	$startBackward = -$N;
186	7	$endBackward = $M;
187
188	7	$V[0][$limit + 1] = 0;
189	7	$V[1][$limit - 1] = $N;
190
191	7	for ($d = 0; $d <= $limit; $d++) {
192	7	$startDiag = \max($valueToAddForward + $startForward, -$d);
193	7	$endDiag = \min($endForward, $d);
194	7	$valueToAddForward = 1 - $valueToAddForward;
195
196		// Compute forward furthest reaching paths.
197	7	for ($k = $startDiag; $k <= $endDiag; $k += 2) {
198	7	if ($k === -$d \|\| ($k < $d && $V[0][$limit + $k - 1] < $V[0][$limit + $k + 1])) {
199	7	$x = $V[0][$limit + $k + 1];
200		} else {
201	7	$x = $V[0][$limit + $k - 1] + 1;
202		}
203
204	7	$y = $x - $k;
205
206	7	$snake[0] = $x + $bottomL1;
207	7	$snake[1] = $y + $bottomL2;
208	7	$snake[2] = 0;
209
210	7	while ($x < $N && $y < $M && $this->isRangeEqual($x + $bottomL1, $y + $bottomL2)) {
211	7	$x++;
212	7	$y++;
213	7	$snake[2]++;
214		}
215
216	7	$V[0][$limit + $k] = $x;
217
218	7	if (!$isEven && $k >= $delta - $d + 1 && $k <= $delta + $d - 1 && $x >= $V[1][$limit + $k - $delta]) {
219	7	return (int) (2 * $d - 1);
220		}
221
222		// Check to see if we can cut down the diagonal range.
223	7	if ($x >= $N && $endForward > $k - 1) {
224	3	$endForward = $k - 1;
225	7	} elseif ($y >= $M) {
226	5	$startForward = $k + 1;
227	5	$valueToAddForward = 0;
228		}
229		}
230
231	7	$startDiag = \max($valueToAddBackward + $startBackward, -$d);
232	7	$endDiag = \min($endBackward, $d);
233	7	$valueToAddBackward = 1 - $valueToAddBackward;
234
235		// Compute backward furthest reaching paths.
236	7	for ($k = $startDiag; $k <= $endDiag; $k += 2) {
237	7	if ($k === $d \|\| ($k !== -$d && $V[1][$limit + $k - 1] < $V[1][$limit + $k + 1])) {
238	7	$x = $V[1][$limit + $k - 1];
239		} else {
240	7	$x = $V[1][$limit + $k + 1] - 1;
241		}
242
243	7	$y = $x - $k - $delta;
244	7	$snake[2] = 0;
245
246	7	while ($x > 0 && $y > 0 && $this->isRangeEqual($x - 1 + $bottomL1, $y - 1 + $bottomL2)) {
247	7	$x--;
248	7	$y--;
249	7	$snake[2]++;
250		}
251
252	7	$V[1][$limit + $k] = $x;
253
254	7	if ($isEven && $k >= -$delta - $d && $k <= $d - $delta && $x <= $V[0][$limit + $k + $delta]) {
255	5	$snake[0] = $bottomL1 + $x;
256	5	$snake[1] = $bottomL2 + $y;
257
258	5	return (int) (2 * $d);
259		}
260
261		// Check to see if we can cut down our diagonal range.
262	7	if ($x <= 0) {
263	3	$startBackward = $k + 1;
264	3	$valueToAddBackward = 0;
265	7	} elseif ($y <= 0 && $endBackward > $k - 1) {
266	5	$endBackward = $k - 1;
267		}
268		}
269		}
270
271		// Computing the true LCS is too expensive, instead find the diagonal with the most progress and pretend a
272		// middle snake of length 0 occurs there.
273		/** @var int[] */
274		$mostProgress = $this->findMostProgress($M, $N, $limit, $V);
275
276		$snake[0] = $bottomL1 + $mostProgress[0];
277		$snake[1] = $bottomL2 + $mostProgress[1];
278		$snake[2] = 0;
279
280		return 5;
281
282		// HACK: since we didn't really finish the LCS computation we don't really know the length of the SES. We don't
283		// do anything with the result anyway, unless it's <=1. We know for a fact SES > 1 so 5 is as good a number as
284		// any to return here.
285		}
286
287		/**
288		* @param int $M
289		* @param int $N
290		* @param int $limit
291		* @param int[][] $V
292		* @return int[]
293		*/
294		private function findMostProgress(int $M, int $N, int $limit, array &$V): array
295		{
296		$delta = $N - $M;
297
298		if (($M & 1) === ($limit & 1)) {
299		$forwardStartDiag = \max(-$M, -$limit);
300		} else {
301		$forwardStartDiag = \max(1 - $M, -$limit);
302		}
303
304		$forwardEndDiag = \min($N, $limit);
305
306		if (($N & 1) === ($limit & 1)) {
307		$backwardStartDiag = \max(-$N, -$limit);
308		} else {
309		$backwardStartDiag = \max(1 - $N, -$limit);
310		}
311
312		$backwardEndDiag = \min($M, $limit);
313		$maxProgress = \array_fill(0,
314		(int) (\max($forwardEndDiag - $forwardStartDiag, $backwardEndDiag - $backwardStartDiag) / 2 + 1),
315		[0, 0, 0]);
316		$numProgress = 0;
317		// the 1st entry is current, it is initialized with 0s.
318
319		// First search the forward diagonals.
320		for ($k = $forwardStartDiag; $k <= $forwardEndDiag; $k += 2) {
321		$x = $V[0][$limit + $k];
322		$y = $x - $k;
323
324		if ($x > $N \|\| $y > $M) {
325		continue;
326		}
327
328		$progress = $x + $y;
329
330		if ($progress > $maxProgress[0][2]) {
331		$numProgress = 0;
332		$maxProgress[0][0] = $x;
333		$maxProgress[0][1] = $y;
334		$maxProgress[0][2] = $progress;
335		} elseif ($progress === $maxProgress[0][2]) {
336		$numProgress++;
337		$maxProgress[$numProgress][0] = $x;
338		$maxProgress[$numProgress][1] = $y;
339		$maxProgress[$numProgress][2] = $progress;
340		}
341		}
342
343		// Progress is in the forward direction.
344		$maxProgressForward = true;
345
346		// Now search the backward diagonals.
347		for ($k = $backwardStartDiag; $k <= $backwardEndDiag; $k += 2) {
348		$x = $V[1][$limit + $k];
349		$y = $x - $k - $delta;
350
351		if ($x < 0 \|\| $y < 0) {
352		continue;
353		}
354
355		$progress = $N - $x + $M - $y;
356
357		if ($progress > $maxProgress[0][2]) {
358		$numProgress = 0;
359		$maxProgressForward = false;
360		$maxProgress[0][0] = $x;
361		$maxProgress[0][1] = $y;
362		$maxProgress[0][2] = $progress;
363		} elseif ($progress === $maxProgress[0][2] && !$maxProgressForward) {
364		$numProgress++;
365		$maxProgress[$numProgress][0] = $x;
366		$maxProgress[$numProgress][1] = $y;
367		$maxProgress[$numProgress][2] = $progress;
368		}
369		}
370
371		// Return the middle diagonal with maximum progress.
372		return $maxProgress[(int) ($numProgress / 2)];
373		}
374
375		/**
376		* @return int
377		*/
378		abstract protected function getLength1(): int;
379
380		/**
381		* @return int
382		*/
383		abstract protected function getLength2(): int;
384
385		/**
386		* @param int $i1
387		* @param int $i2
388		* @return bool
389		*/
390		abstract protected function isRangeEqual(int $i1, int $i2): bool;
391
392		/**
393		* @param int $sl1
394		* @param int $sl2
395		* @return void
396		*/
397		abstract protected function setLcs(int $sl1, int $sl2): void;
398
399		/**
400		* @param int $lcsLength
401		* @return void
402		*/
403		abstract protected function initializeLcs(int $lcsLength): void;
404		}
405

snebes / php-daisydiff

LCS::findMiddleSnake() F last analyzed 2019-09-10 16:50 UTC

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LCS::findMiddleSnake() F
last analyzed 2019-09-10 16:50 UTC