C++ – How to remove an item from a stl vector with a certain value

EDIT: using c++14, the best solution is very easy to write thanks to lambdas that can now have parameters of type auto. This is my current favorite solution

std::sort(v.begin(), v.end(), [](auto &left, auto &right) {
    return left.second < right.second;
});

ORIGINAL ANSWER:

Just use a custom comparator (it's an optional 3rd argument to std::sort)

struct sort_pred {
    bool operator()(const std::pair<int,int> &left, const std::pair<int,int> &right) {
        return left.second < right.second;
    }
};

std::sort(v.begin(), v.end(), sort_pred());

If you're using a C++11 compiler, you can write the same using lambdas:

std::sort(v.begin(), v.end(), [](const std::pair<int,int> &left, const std::pair<int,int> &right) {
    return left.second < right.second;
});

EDIT: in response to your edits to your question, here's some thoughts ... if you really wanna be creative and be able to reuse this concept a lot, just make a template:

template <class T1, class T2, class Pred = std::less<T2> >
struct sort_pair_second {
    bool operator()(const std::pair<T1,T2>&left, const std::pair<T1,T2>&right) {
        Pred p;
        return p(left.second, right.second);
    }
};

then you can do this too:

std::sort(v.begin(), v.end(), sort_pair_second<int, int>());

or even

std::sort(v.begin(), v.end(), sort_pair_second<int, int, std::greater<int> >());

Though to be honest, this is all a bit overkill, just write the 3 line function and be done with it :-P

You don't have to write a completely new container class. You can stick with your STL containers, but change the second parameter of for example std::vector to give it your custom allocator which allocates from a stack-buffer. The chromium authors wrote an allocator just for this:

https://chromium.googlesource.com/chromium/chromium/+/master/base/stack_container.h

It works by allocating a buffer where you say how big it is. You create the container and call container.reserve(buffer_size);. If you overflow that size, the allocator will automatically get elements from the heap (since it is derived from std::allocator, it will in that case just use the facilities of the standard allocator). I haven't tried it, but it looks like it's from google so i think it's worth a try.

Usage is like this:

StackVector<int, 128> s;
s->push_back(42); // overloaded operator->
s->push_back(43);

// to get the real std::vector. 
StackVector<int, 128>::ContainerType & v = s.container();
std::cout << v[0] << " " << v[1] << std::endl;