2017-11

2017/11.cpp

@@ -0,0 +1,100 @@
+#include <array>
+#include <bit>
+#include <cstdint>
+#include <iostream>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include <doctest.h>
+
+#include <aocpp/Startup.hpp>
+#include <aocpp/Parsing.hpp>
+
+namespace {
+
+/*
+  \ n  /
+nw +--+ ne
+  /    \
+-+      +-
+  \    /
+sw +--+ se
+  / s  \
+*/
+
+struct Hex {
+  std::int64_t q, r, s;
+};
+
+constexpr Hex HEX_N  {  0, -1,  1 };
+constexpr Hex HEX_NE {  1, -1,  0 };
+constexpr Hex HEX_SE {  1,  0, -1 };
+constexpr Hex HEX_S  {  0,  1, -1 };
+constexpr Hex HEX_SW { -1,  1,  0 };
+constexpr Hex HEX_NW { -1,  0,  1 };
+
+auto operator+(Hex a, Hex b) -> Hex {
+  return {a.q + b.q, a.r + b.r, a.s + b.s };
+}
+
+auto operator+=(Hex & a, Hex b) -> Hex & {
+  a.q += b.q; a.r += b.r; a.s += b.s;
+  return a;
+}
+
+auto hex_distance(Hex hex) -> std::int64_t {
+  return (std::abs(hex.q) + std::abs(hex.r) + std::abs(hex.s)) / 2;
+}
+
+auto Walk(std::string const& commands)
+-> std::pair<std::int64_t, std::int64_t>
+{
+  Hex here {};
+  std::int64_t part2 = 0;
+  for (auto const& command : aocpp::SplitOn(commands, ",")) {
+    here +=
+      "n"  == command ? HEX_N  :
+      "ne" == command ? HEX_NE :
+      "nw" == command ? HEX_NW :
+      "s"  == command ? HEX_S  :
+      "se" == command ? HEX_SE :
+      "sw" == command ? HEX_SW :
+      throw std::runtime_error{"bad input"};
+    part2 = std::max(part2, hex_distance(here));
+  }
+  return {hex_distance(here), part2};
+}
+
+} // namespace
+
+TEST_SUITE("2017-11 examples") {
+  TEST_CASE("example 1") {
+    auto [p1,p2] = Walk("ne,ne,ne");
+    CHECK(p1 == 3);
+    CHECK(p2 == 3);
+  }
+  TEST_CASE("example 2") {
+    auto [p1,p2] = Walk("ne,ne,sw,sw");
+    CHECK(p1 == 0);
+    CHECK(p2 == 2);
+  }
+  TEST_CASE("example 3") {
+    auto [p1,p2] = Walk("ne,ne,s,s");
+    CHECK(p1 == 2);
+    CHECK(p2 == 2);
+  }
+  TEST_CASE("example 4") {
+    auto [p1,p2] = Walk("se,sw,se,sw,sw");
+    CHECK(p1 == 3);
+    CHECK(p2 == 3);
+  }
+}
+
+auto main(int argc, char** argv) -> int {
+  std::string line;
+  std::getline(*aocpp::Startup(argc, argv), line);
+  auto [part1, part2] = Walk(line);
+  std::cout << "Part 1: " << part1 << std::endl;
+  std::cout << "Part 2: " << part2 << std::endl;
+}

2017/14.cpp

@@ -9,20 +9,18 @@
 #include <doctest.h>
 
 #include <aocpp/Startup.hpp>
-#include <aocpp/Parsing.hpp>
 #include <knothash.hpp>
 
 namespace {
 
-using Grid = std::vector<std::array<std::uint8_t, 16>>;
+using Grid = std::array<std::array<std::uint8_t, 16>, 128>;
 
 auto MakeRows(std::string input) -> Grid {
   Grid rows;
-  rows.reserve(128);
 
   input += "-";
   for (int i = 0; i < 128; i++) {
-    rows.emplace_back(knothash::hash(input + std::to_string(i)));
+    rows[i] = knothash::hash(input + std::to_string(i));
   }
 
   return rows;

2017/CMakeLists.txt

@@ -7,6 +7,9 @@ target_link_libraries(2017_06 aocpp)
 add_executable(2017_10 10.cpp)
 target_link_libraries(2017_10 aocpp knothash)
 
+add_executable(2017_11 11.cpp)
+target_link_libraries(2017_11 aocpp)
+
 add_executable(2017_14 14.cpp)
 target_link_libraries(2017_14 aocpp knothash)