q4.cpp

#include <list>
#include <algorithm>
#include <iostream>
using namespace std;

template <class T>
typename list<T>::iterator _erase(list<T> &l, const T &val)
{
    auto it = find(l.begin(), l.end(), val);
    if (it == l.end())
        return it;

    l.erase(it);
    return ++it;
}

int main()
{
    list<int> l{12, 41, 41, 76, 90};
    auto it = _erase(l, 12);

    copy(l.begin(), l.end(), ostream_iterator<int>(cout, ", "));
    cout << '\n';

    std::cout << *it;
}