Created
September 28, 2019 21:01
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My solution to: https://coderbyte.com/editor/guest:Maximal%20Square:PHP
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<?php | |
declare(strict_types=1); | |
/** | |
* Class MaxSquareFinder | |
* | |
*/ | |
class MaxSquareFinder | |
{ | |
/** | |
* Square array | |
* | |
* @var string[] $_square | |
*/ | |
protected $_square; | |
/** | |
* Square line length | |
* | |
* @var int $_lineLength | |
*/ | |
protected $_lineLength; | |
/** | |
* Square row count | |
* | |
* @var int rowCount | |
*/ | |
protected $_rowCount; | |
/** | |
* Set square array | |
* | |
* @param array $_square | |
*/ | |
public function setSquare(array $_square): void | |
{ | |
$this->_square = $_square; | |
$this->_lineLength = strlen($this->_square[0]); | |
$this->_rowCount = count($this->_square); | |
} | |
/** | |
* Return size of largest square of '1's found in square array | |
* | |
* @return int | |
*/ | |
public function findLargestSquare(): int | |
{ | |
$searchLength = min($this->_lineLength, $this->_rowCount); | |
while ($searchLength >= 1) { | |
$currentRow = 0; | |
$search = str_repeat('1', $searchLength); | |
while ($currentRow < $this->_rowCount) { | |
foreach (self::_strpos_all($this->_square[$currentRow], $search) as $pos) { | |
if ($this->_checkPosBelow($pos, $currentRow, $searchLength, $search)) { | |
return $searchLength ** 2; | |
} | |
} | |
$currentRow++; | |
} | |
$searchLength--; | |
} | |
return 0; | |
} | |
/** | |
* Checks if square array has size times '1' below given pos/row | |
* | |
* @param int $row Row | |
* @param int $pos Pos | |
* @param int $size Size | |
* @param string $search Search string | |
* @return bool | |
*/ | |
protected function _checkPosBelow(int $row, int $pos, int $size, string $search): bool | |
{ | |
$nextRow = $row + 1; | |
while ($nextRow < $row + $size) { | |
$rowPos = strpos($this->_square[$nextRow], $search, $pos); | |
if ($rowPos !== 0) { | |
return false; | |
} | |
$nextRow++; | |
} | |
return true; | |
} | |
/** | |
* Find all positions of needle in haystack | |
* | |
* @param string $haystack Haystack | |
* @param string $needle Needle | |
* @return array | |
*/ | |
protected static function _strpos_all(string $haystack, string $needle): array | |
{ | |
$offset = 0; | |
$allpos = array(); | |
while (($pos = strpos($haystack, $needle, $offset)) !== FALSE) { | |
$offset = $pos + 1; | |
$allpos[] = $pos; | |
} | |
return $allpos; | |
} | |
} |
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