2020/10

2020/10.cpp

@@ -0,0 +1,82 @@
+#include <cstdint>
+#include <iostream>
+#include <sstream>
+#include <tuple>
+#include <vector>
+
+#include <doctest.h>
+
+#include <aocpp/Startup.hpp>
+
+namespace {
+
+// Parses the numbers and returns them in sorted order
+auto Parse(std::istream & in) -> std::vector<std::int64_t>
+{
+  std::vector<std::int64_t> result;
+  std::int64_t value;
+  while (in >> value) {
+    result.push_back(value);
+  }
+  std::sort(result.begin(), result.end());
+  return result;
+}
+
+auto Part1(std::vector<std::int64_t> const& adapters) -> std::size_t
+{
+  std::int64_t prev{0};
+  std::size_t ones{0}, threes{1};
+  if (adapters.empty()) return 0;
+  for (auto const x : adapters) {
+    switch (x - prev) {
+    case 1: ones++; break;
+    case 3: threes++; break;
+    }
+    prev = x;
+  }
+  return ones * threes;
+}
+
+auto Part2(std::vector<std::int64_t> const& adapters) -> std::size_t
+{
+  std::size_t n1{1}, n2{0}, n3{0};
+  std::int64_t prev{0};
+
+  for (auto const x : adapters) {
+    switch(x - prev) {
+      case 1:  std::tie(n1,n2,n3) = std::make_tuple(n1+n2+n3, n1, n2); break;
+      case 2:  std::tie(n1,n2,n3) = std::make_tuple(n1+n2,     0, n1); break;
+      case 3:  std::tie(n1,n2,n3) = std::make_tuple(n1,        0,  0); break;
+      default: std::tie(n1,n2,n3) = std::make_tuple(0       ,  0,  0); break;
+    }
+    prev = x;
+  }
+
+  return n1;
+}
+
+} // namespace
+
+TEST_SUITE("documented examples") {
+
+TEST_CASE("part 1") {
+  std::istringstream in {"16 10 15 5 1 11 7 19 6 12 4"};
+  REQUIRE(Part1(Parse(in)) == 7*5);
+  in = std::istringstream{"28 33 18 42 31 14 46 20 48 47 24 23 49 45 19 38 39 11 1 32 25 35 8 17 7 9 4 2 34 10 3 "};
+  REQUIRE(Part1(Parse(in)) == 22*10);
+}
+
+TEST_CASE("part 2") {
+  std::istringstream in {"16 10 15 5 1 11 7 19 6 12 4"};
+  REQUIRE(8 == Part2(Parse(in)));
+  in = std::istringstream{"28 33 18 42 31 14 46 20 48 47 24 23 49 45 19 38 39 11 1 32 25 35 8 17 7 9 4 2 34 10 3 "};
+  REQUIRE(19208 == Part2(Parse(in)));
+}
+
+}
+
+auto main(int argc, char** argv) -> int {
+  auto adapters = Parse(aocpp::Startup(argc, argv));
+  std::cout << "Part 1: " << Part1(adapters) << std::endl;
+  std::cout << "Part 2: " << Part2(adapters) << std::endl;
+}

2020/CMakeLists.txt

@@ -4,6 +4,9 @@ target_link_libraries(2020_02 aocpp)
 add_executable(2020_03 03.cpp)
 target_link_libraries(2020_03 aocpp)
 
+add_executable(2020_10 10.cpp)
+target_link_libraries(2020_10 aocpp)
+
 add_executable(2020_16 16.cpp)
 target_link_libraries(2020_16 aocpp dlx)