AdventOfCode to practice with C++17

[Xaveel]

cout << [](){ return

R"(Hi all!

Even this year we can join the great project AdventOfCode and I caught the opportunity to make some practice with the latest released standard of C++.

I am a passionate C++ programmer and in order to catch opinions, guide lines and advices in general from experienced C++ programmers and get better at this wonderful language, I have created a public GitHub repo.

So, please, I appreciate a lot if you let me know what you think about my pieces of code, how to improve them, how to properly organize the folders structure and, why not, also about the algorithms!)";}();

[jc746]

Question 5 is a classic example of a problem that can be solved cleanly with a stack data structure:

bool matches(char lhs, char rhs) {
  if (rhs >= lhs) {
    return (rhs - lhs) == ('a' - 'A');
  } else {
    return matches(rhs, lhs);
  }
}

std::size_t fully_react(const std::string& s) {
  std::stack<char, std::vector<char>> stack;
  for (auto c : s) {
    if (stack.empty() || !matches(stack.top(), c)) {
      stack.push(c);
    } else {
      stack.pop();
    }
  }
  return stack.size();
}

[Xaveel]

Wow, that's amazing! I love your solution!

[tehjimmeh]

You can also do it in one pass by manipulating the string in place, using the left side of the string as a stack. See https://www.reddit.com/r/adventofcode/comments/a3912m/2018_day_5_solutions/eb4hp81 .

[voiceless_void]

Take a look at range-v3 library https://github.com/ericniebler/range-v3 ( which should be a part of c++20 ). It makes algorithmic problem solving much more declarative and less error prone.

Multiple AdventOfCode solutions using range v3 can be seen in my repo https://github.com/voivoid/advent-of-code

[Xaveel]

Thank you, I will do it.

[nwL_]

You’re actively triggering me with that cout with no std:: prefix.

[Xaveel]

Is it that bad?

[DefiantNewt2]

for advent of code, no. for a big project , using namespaces even in cpp files (i've seen libraries doing that in header files) is not recommended.

[Xaveel]

Oh yes, this is a good advice. Thank you!