Function FindIndex

util/generic/algorithm.h:195–200

template <class C, class T>
constexpr size_t FindIndex(C&& c, const T& x) {
    using std::begin;
    using std::end;
    auto it = Find(begin(c), end(c), x);
    return it == end(c) ? NPOS : (it - begin(c));
}

template <class C, class P>
constexpr size_t FindIndexIf(C&& c, P p) {