aocpp/knothash/src/knothash.cpp

#include <knothash.hpp>

#include <numeric>
#include <iomanip>
#include <sstream>

#include <doctest.h>

namespace knothash {

auto hash(std::string key) -> std::array<std::uint8_t, 16>
{
  key += 17;
  key += 31;
  key += 73;
  key += 47;
  key += 23;
  auto sparse = hash_ex<256>(64, key.begin(), key.end());

  std::size_t offset = 0;
  std::array<std::uint8_t, 16> dense;
  for (auto & x : dense) {
    x = std::reduce(sparse.begin()+offset, sparse.begin()+offset+16, 0, std::bit_xor());
    offset += 16;
  } 

  return dense;
}

auto render(std::array<std::uint8_t, 16> const& hash) -> std::string {
  std::ostringstream out;
  out << std::hex << std::setfill('0');
  for (int const x : hash) {
    out << std::setw(2) << int(x);
  }
  return out.str();
}

TEST_SUITE("knothash library") {

TEST_CASE("reverser") {
  std::array<std::uint8_t, 9> v {0,1,2,3,4,5,6,7,8};

  SUBCASE("more left") {
    std::array<std::uint8_t, 9> expect {1,0,8,7,4,5,6,3,2};
    reverser(v, 7, 6);
    CHECK(v == expect);
  }

  SUBCASE("more right") {
    std::array<std::uint8_t, 9> expect {6,5,2,3,4,1,0,8,7};
    reverser(v, 5, 6);
    CHECK(v == expect);
  }

  SUBCASE("middle") {
    std::array<std::uint8_t, 9> expect {0,1,5,4,3,2,6,7,8};
    reverser(v, 2, 4);
    CHECK(v == expect);
  }
}

TEST_CASE("knot example") {
  std::array<std::size_t, 4> lengths {3, 4, 1, 5};
  auto result = hash_ex<5>(1, lengths.begin(), lengths.end());
  std::array<std::uint8_t, 5> expected {3, 4, 2, 1, 0};
  CHECK(result == expected);
}

TEST_CASE("hash examples") {
  CHECK(render(hash(""))         == "a2582a3a0e66e6e86e3812dcb672a272");
  CHECK(render(hash("AoC 2017")) == "33efeb34ea91902bb2f59c9920caa6cd");
  CHECK(render(hash("1,2,3"))    == "3efbe78a8d82f29979031a4aa0b16a9d");
  CHECK(render(hash("1,2,4"))    == "63960835bcdc130f0b66d7ff4f6a5a8e");
}

}

} // namespace