Notes.md

C++ Notes

set_union

set_union is useful to find an union of two sorted vectors, where result is also sorted:

set_union(first.begin(), first.end(), 
          second.begin(), second.end(), 
          result.begin());

back_inserter

The push_back is called whenever the iterator is assigned to. It is really useful using it with other STL algorithms.

optional

std::optional contains a value or not. It can be used with if:

if (auto value = get_optional_value()) {
  std::cout << *value;
}

• nullopt used for the absent value.
• value_or is useful for getting the value or the specified value.

list

• list::splice concatenates two lists in O(1) time, without any copying of data.
• list::insert inserts elements by copying elements in O(n) time.

random

• std::random_device can be used to seed a random number generator.
  • or a time.
• std::mt19937 - is a pseudo-random generator of 32-bit numbers.
• std::uniform_int_distribution<int> - uniform discrete distribution. An instance of std::mt19937 must passed.

sample

std::random_device rd();
std::mt19937 rng(rd());
std::sample(in.begin(), in.end(), std::back_inserter(out), 5, rng);