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C++: Find Common Directory Path

Bjarne-stroustrup
 

Create a routine that, given a set of strings representing directory paths and a single character directory separator, will return a string representing that part of the directory tree that is common to all the directories.

Test your routine using the forward slash ‘/’ character as the directory separator and the following three strings as input paths:

 '/home/user1/tmp/coverage/test'
 '/home/user1/tmp/covert/operator'
 '/home/user1/tmp/coven/members'

Note: The resultant path should be the valid directory '/home/user1/tmp' and not the longest common string '/home/user1/tmp/cove'.
If your language has a routine that performs this function (even if it does not have a changeable separator character), then mention it as part of the task.

#include <algorithm>
#include <iostream>
#include <string>
#include <vector>

std::string longestPath( const std::vector<std::string> & , char ) ;

int main( ) {
	std::string dirs[ ] = {
		"/home/user1/tmp/coverage/test" ,
		"/home/user1/tmp/covert/operator" ,
		"/home/user1/tmp/coven/members" } ;
	std::vector<std::string> myDirs ( dirs , dirs + 3 ) ;
	std::cout << "The longest common path of the given directories is "
	<< longestPath( myDirs , '/' ) << "!\n" ;
	return 0 ;
}

std::string longestPath( const std::vector<std::string> & dirs , char separator ) {
	std::vector<std::string>::const_iterator vsi = dirs.begin( ) ;
	int maxCharactersCommon = vsi->length( ) ;
	std::string compareString = *vsi ;
	for ( vsi = dirs.begin( ) + 1 ; vsi != dirs.end( ) ; vsi++ ) {
		std::pair<std::string::const_iterator , std::string::const_iterator> p = 
		std::mismatch( compareString.begin( ) , compareString.end( ) , vsi->begin( ) ) ;
		if (( p.first - compareString.begin( ) ) < maxCharactersCommon ) 
		maxCharactersCommon = p.first - compareString.begin( ) ;
	}
	std::string::size_type found = compareString.rfind( separator , maxCharactersCommon ) ;
	return compareString.substr( 0 , found ) ;
}

Output:

The longest common path of the given directories is /home/user1/tmp!

SOURCE

Content is available under GNU Free Documentation License 1.2.