Removing alternate elements in a List

Question

What is the most efficient way to remove alternate (odd indexed or even indexed) elements in an List without using a place holder list variable?

A

Answer 1

I would use the standard pattern generally used for STL containers. Do a remove followed by an erase.

This way you will not confuse people that are used to seeing this pattern.

template
struct RemoveEven
{
    RemoveEven():count(0)   {}
    bool operator()(T const&)
    {
        bool    result  =  count%2 == 0;
        count++;
        return result;
    }
    private:
        std::size_t count;
};
int main()
{
    std::list  a;
    a.erase(std::remove_if(a.begin(),a.end(),RemoveEven()),a.end());

}