Step by Step solution about How to resolve the algorithm Find common directory path step by step in the PHP programming language

The provided PHP scripts define two functions, _commonPath and getCommonPath, that are designed to find and return the common path shared by a given set of directory paths. Here's a detailed explanation of each function:

1. _commonPath function:

• This function takes an array of directory paths, $dirList, as input.
• It initializes an empty array, $arr, to keep track of the number of directory components in each path.
• It iterates over the input paths, splits each path into its components (using the / character as a delimiter), and removes the leading empty component (the root directory).
• For each path, it counts the number of directory components and stores it in the $arr array.
• It finds the minimum number of directory components among all the paths and stores it in the $min variable.
• It iterates over the paths again, removing the extra components from each path to align them with the $min value.
• It converts each trimmed path back to a string using the / character as a separator and stores it back in $dirList.
• It removes any duplicate paths from $dirList.
• It repeatedly applies the dirname() function to remove the last directory component from each path until only one unique path remains.
• Finally, it returns the common path shared by all the input paths.

2. getCommonPath function:

• This function is a more compact and efficient version of the _commonPath function, designed for string paths. It assumes that the input paths are strings and does not handle trailing slashes.
• It initializes the $lastOffset variable to 1, which represents the starting position after the root directory.
• It initializes the $common variable to '/', which represents the root directory.
• It iterates through the characters of the first path in $paths.
• For each character, it checks if it is a / and if it is not the first character in the path. If these conditions are met, it means a directory component has ended.
• It extracts the current directory component from the path and checks if it matches the same component in all other paths in $paths. If it doesn't match, it returns the $common path, which represents the common path up to that point.
• If all paths have the same directory component, it appends that component to the $common path and updates the $lastOffset to the next character after the directory component.
• It continues this process until there are no more directory components in the first path.
• Finally, it returns the $common path, which represents the common path shared by all the input paths, excluding any trailing slash.

Both functions aim to identify and return the longest common path that is shared by a set of directory paths. They can be useful in various scenarios, such as comparing file paths, identifying shared directories, or performing file system operations.

<?php

/*
 This works with dirs and files in any number of combinations.
*/

function _commonPath($dirList)
{
	$arr = array();
	foreach($dirList as $i => $path)
	{
		$dirList[$i]	= explode('/', $path);
		unset($dirList[$i][0]);
		
		$arr[$i] = count($dirList[$i]);
	}
	
	$min = min($arr);
	
	for($i = 0; $i < count($dirList); $i++)
	{
		while(count($dirList[$i]) > $min)
		{
			array_pop($dirList[$i]);
		}
		
		$dirList[$i] = '/' . implode('/' , $dirList[$i]);
	}
	
	$dirList = array_unique($dirList);
	while(count($dirList) !== 1)
	{
		$dirList = array_map('dirname', $dirList);
		$dirList = array_unique($dirList);
	}
	reset($dirList);
	
	return current($dirList);
}

 /* TEST */

$dirs = array(
 '/home/user1/tmp/coverage/test',
 '/home/user1/tmp/covert/operator',
 '/home/user1/tmp/coven/members',
);


if('/home/user1/tmp' !== common_path($dirs))
{
  echo 'test fail';
} else {
  echo 'test success';
}

?>


<?php

/* A more compact string-only version, which I assume would be much faster */
/* If you want the trailing /, return $common; */

function getCommonPath($paths) {
	$lastOffset = 1;
	$common = '/';
	while (($index = strpos($paths[0], '/', $lastOffset)) !== FALSE) {
		$dirLen = $index - $lastOffset + 1;	// include /
		$dir = substr($paths[0], $lastOffset, $dirLen);
		foreach ($paths as $path) {
			if (substr($path, $lastOffset, $dirLen) != $dir)
				return $common;
		}
		$common .= $dir;
		$lastOffset = $index + 1;
	}
	return substr($common, 0, -1);
}

?>