Re: erase vector v2 elements from v1

From:

Obnoxious User <OU@127.0.0.1>

Newsgroups:

comp.lang.c++

Date:

Sun, 04 Jan 2009 12:56:26 -0600

Message-ID:

<tYSdnVsqb8_Hm_zUnZ2dnUVZ8uednZ2d@giganews.com>

On Sun, 04 Jan 2009 09:57:32 -0800, James Juno wrote:

Hi folks,

Rudimentary container question. I have something like

    std::vector<int> v1;
    std::vector<int> v2;

I want to remove all elements in v2 from v1. Right now I'm using this
horrible non-STL loop:

    for ( size_t i = 0; i < v1.size(); ++i ) for ( size_t j = 0; j <
    v2.size(); ++j ) {
        if ( v1[i] == v2[j] )
        {
            v1.erase( v1.begin() + i );
            break;
        }
    }

Yuck. There has got to be a cleaner, more STL-like way of doing this.

#include <iterator>
#include <algorithm>
template<typename Container>
void exclude(Container & values, Container & remove, Container & output) {
    /*
        If 'values' and 'remove' already are sorted, then
        these two calls can be removed and you can add 'const'
        in the parameter list. Or create sorted temporaries.
    */
    std::sort(values.begin(),values.end());
    std::sort(remove.begin(),remove.end());
    std::set_difference(values.begin(),values.end(),
        remove.begin(),remove.end(),std::back_inserter(output));
}

--
OU