aocpp/2017/19.cpp

#include <cstdint>
#include <cctype>
#include <iostream>
#include <sstream>
#include <string>
#include <tuple>
#include <vector>

#include <doctest.h>

#include <aocpp/Startup.hpp>
#include <aocpp/Grid.hpp>
#include <aocpp/Coord.hpp>

using namespace aocpp;

namespace {

auto Drive(Grid const& grid) -> std::pair<std::string, int>
{
  std::string path;
  int steps = 0;

  Coord here {};
  Coord dir {0,1};

  // Find starting column
  for (std::size_t i = 0; i < grid.rows[0].size(); i++) {
    if (grid.rows[0][i] != ' ') {
      here.x = i;
      break;
    }
  }

  for(;;) {
    char c = grid[here];
    if (c == '+') {
      if (grid[here + CW(dir)] != ' ') {
        dir = CW(dir);
      } else if (grid[here + CCW(dir)] != ' ') {
        dir = CCW(dir);
      }
    } else if (c == ' ') {
      break;
    } else if (std::isalpha(c)) {
      path += c;
    }
    steps++;
    here += dir;
  }

  return {path, steps};
}

} // namespace

TEST_SUITE("2017-19 examples") {
  TEST_CASE("example") {
    std::istringstream in {
      "     |          \n"
      "     |  +--+    \n"
      "     A  |  C    \n"
      " F---|--|-E---+ \n"
      "     |  |  |  D \n"
      "     +B-+  +--+ \n"
      "                \n"
    };
    auto const [p1, p2] = Drive(Grid::Parse(in));
    CHECK(p1 == "ABCDEF");
    CHECK(p2 == 38);
  }
}

auto Main(std::istream & in, std::ostream & out) -> void
{
  auto const [part1, part2] = Drive(Grid::Parse(in));
  out << "Part 1: " << part1 << std::endl;
  out << "Part 2: " << part2 << std::endl;
}