Re: Quicksort for list of string

<aparnakakkar2003@gmail.com> wrote in message
news:1176983446.882491.29820@p77g2000hsh.googlegroups.com...


Well, this doesn't use quicksort but std::sort which is O( N log N ).

Output is:

Before sort:
ABC
abc
BBC
ABCD
aB

After sort:
ABC
ABCD
BBC
aB
abc

After Case Insensitive sort:
aB
ABC
abc
ABCD
BBC

There may be a better/faster algorithm for the case insensitve comparing of
std::strings. I just did this one rather quickly.

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

bool CILessthan( const std::string Elem1, const std::string Elem2 )
{
    for ( std::size_t i = 0; i < Elem1.length(); ++i )
    {
        if ( std::tolower( Elem1[i] ) < std::tolower( Elem2[i] ) )
            return true;
        else if ( std::tolower( Elem1[i] ) > std::tolower( Elem2[i] ) )
            return false;
    }

    // Equal up to this point, but one may be longer
    if ( Elem1.length() < Elem2.length() )
        return true;

    return false;
}

void ShowData( const std::vector<std::string>& Data )
{
    for ( std::vector<std::string>::const_iterator it = Data.begin(); it !=
Data.end(); ++it )
        std::cout << (*it) << "\n";
}

int main()
{
    std::vector<std::string> Data;
    Data.push_back( "ABC" );
    Data.push_back( "abc" );
    Data.push_back( "BBC" );
    Data.push_back( "ABCD" );
    Data.push_back( "aB" );

    std::cout << "Before sort:\n";
    ShowData( Data );

    std::sort( Data.begin(), Data.end() );
    std::cout << "\nAfter sort:\n";
    ShowData( Data );

    std::sort( Data.begin(), Data.end(), CILessthan );
    std::cout << "\nAfter Case Insensitive sort:\n";
    ShowData( Data );

    std::string wait;
    std::getline( std::cin, wait );
}