STL list, delete all the odd numbers

Question

I am trying to learn how to work with STL and tried to write a function which will recieve a refference to a list and will try to delete all odd members. I am having a sligh

Answer 1

Method erase returns iterator to the next element after deleted. So the usual approach to such a task is the following

void removeOdds( std::list &myvector )
{
    for ( auto it = myvector.begin(); it != myvector.end();  )
    {
        if ( *it % 2 !=0 )
        {
            it = myvector.erase( it );
        }
        else
        {
            ++it;
        }
    }
}

As for your code then the loop statement always increases the iterator

for(list::iterator p=myvector.begin(); p !=myvector.end();p++)
                                                               ^^^^  

Take into account that class std::list has methods remove and remove_if that erase all elements that satisfy the given criteria.

Here is a demonstrative program that shows the both approaches

#include 
#include 

void removeOdds( std::list &myvector )
{
    for ( auto it = myvector.begin(); it != myvector.end();  )
    {
        if ( *it % 2 !=0 )
        {
            it = myvector.erase( it );
        }
        else
        {
            ++it;
        }
    }
}

int main()
{
    std::list l = { 1, 3, 5, 2, 6, 7 };

    for ( auto x : l ) std::cout << x << ' ';
    std::cout << std::endl;

    removeOdds( l );

    for ( auto x : l ) std::cout << x << ' ';
    std::cout << std::endl;

    l = { 1, 3, 5, 2, 6, 7 };

    for ( auto x : l ) std::cout << x << ' ';
    std::cout << std::endl;

    l.remove_if( []( int x ) { return x % 2; } );

    for ( auto x : l ) std::cout << x << ' ';
    std::cout << std::endl;
}

The program output is

1 3 5 2 6 7 
2 6 
1 3 5 2 6 7 
2 6