fiddle

2022/01.cpp

@@ -38,16 +38,24 @@ auto Parse(std::istream & in) -> Input
 /// @return top 1 and sum of top 3 calorie counts
 auto Solve(Input const& input) -> std::pair<std::int64_t, std::int64_t>
 {
-  if (input.size() < 3) { throw std::runtime_error{"bad input"}; }
-
-  std::vector<std::int64_t> elves;
-  for (auto const& elf : input) {
-    elves.push_back(std::reduce(elf.begin(), elf.end()));
+  if (input.size() < 3) {
+    throw std::runtime_error{"bad input"};
   }
 
-  std::partial_sort(elves.begin(), std::next(elves.begin(), 3), elves.end(), std::greater());
+  std::vector<std::int64_t> elves;
+  std::transform(
+    input.begin(), input.end(), std::back_inserter(elves),
+    [](auto const& elf){
+      return std::reduce(elf.begin(), elf.end());
+    });
 
-  return {elves.front(), std::reduce(elves.begin(), std::next(elves.begin(), 3))};
+  // Fill the top 3 array elements with the maximum values
+  auto const top3 = std::next(elves.begin(), 3);
+  std::partial_sort(elves.begin(), top3, elves.end(), std::greater());
+
+  auto const p1 = elves.front();
+  auto const p2 = std::reduce(elves.begin(), top3);
+  return {p1, p2};
 }
 
 } // namespace
@@ -69,15 +77,15 @@ TEST_SUITE("2022-01 examples") {
       "9000\n"
       "\n"
       "10000\n"};
-    auto entries = Parse(in);
-    auto [p1,p2] = Solve(entries);
+    auto const entries = Parse(in);
+    auto const [p1,p2] = Solve(entries);
     CHECK(p1 == 24000);
     CHECK(p2 == 45000);
   }
 }
 
 auto main(int argc, char** argv) -> int {
-  auto [p1,p2] = Solve(Parse(*aocpp::Startup(argc, argv)));
+  auto const [p1,p2] = Solve(Parse(*aocpp::Startup(argc, argv)));
   std::cout << "Part 1: " << p1 << std::endl;
   std::cout << "Part 2: " << p2 << std::endl;
 }

2022/03.cpp

@@ -9,6 +9,8 @@
 #include <vector>
 #include <string_view>
 
+#include <boost/range/irange.hpp>
+
 #include <doctest.h>
 
 #include <aocpp/Startup.hpp>
@@ -30,42 +32,52 @@ auto Priority(char const c) -> std::int64_t
   return c < 'a' ? c-'A'+27 : c-'a'+1;
 }
 
-auto Intersect(std::string const& a, std::string const& b) {
+auto Intersect(
+  std::string::const_iterator start1, std::string::const_iterator end1,
+  std::string::const_iterator start2, std::string::const_iterator end2
+) -> std::string
+{
   std::string common;
-  std::set_intersection(a.begin(), a.end(), b.begin(), b.end(),
+  std::set_intersection(
+    start1, end1,
+    start2, end2,
     std::back_inserter(common));
   return common;
 }
 
-auto Part1(std::vector<std::string> const& input) -> std::int64_t
+auto Part1(std::vector<std::string> & input) -> std::int64_t
 {
-  std::int64_t n {0};
-  for (auto const& line : input) {
-    auto m = line.size() / 2;
-
-    auto elf1 {line.substr(0, m)};
-    std::sort(elf1.begin(), elf1.end());
-
-    auto elf2 {line.substr(m)};
-    std::sort(elf2.begin(), elf2.end());
-
-    n += Priority(Intersect(elf1, elf2).at(0));
-  }
-  return n;
+  return std::transform_reduce(
+    input.begin(), input.end(),
+    std::int64_t{0}, std::plus(), // sum
+    [](auto & line) {
+      auto const mid = line.begin() + line.size() / 2;
+      std::sort(line.begin(), mid);
+      std::sort(mid, line.end());
+      auto const common = Intersect(line.begin(), mid, mid, line.end());
+      return Priority(common.at(0));
+    });
 }
 
-auto Part2(std::vector<std::string> input) -> std::int64_t
+auto Part2(std::vector<std::string> & input) -> std::int64_t
 {
-  std::int64_t n {0};
-
   for (auto & line : input) {
     std::sort(line.begin(), line.end());
   }
 
-  for (std::size_t i = 0; i + 2 < input.size(); i += 3) {
-    n += Priority(Intersect(Intersect(input[i], input[i+1]), input[i+2]).at(0));
-  }
-  return n;
+  auto const range = boost::irange<std::size_t>(0, input.size(), 3);
+  return std::transform_reduce(
+    range.begin(), range.end(),
+    std::int64_t{0}, std::plus(), // sum
+    [&input](auto const i) {
+      auto const input01 = Intersect(
+        input[i  ].begin(), input[i  ].end(),
+        input[i+1].begin(), input[i+1].end());
+      auto const input012 = Intersect(
+        input01   .begin(), input01   .end(),
+        input[i+2].begin(), input[i+2].end());
+      return Priority(input012.at(0));
+    });
 }
 
 } // namespace
@@ -81,12 +93,12 @@ TEST_SUITE("2022-03 examples") {
       "CrZsJsPPZsGzwwsLwLmpwMDw\n"};
     auto input = Parse(in);
     CHECK(Part1(input) == 157);
-    CHECK(Part2(std::move(input)) == 70);
+    CHECK(Part2(input) == 70);
   }
 }
 
 auto main(int argc, char** argv) -> int {
   auto input = Parse(*aocpp::Startup(argc, argv));
   std::cout << "Part 1: " << Part1(input) << std::endl;
-  std::cout << "Part 2: " << Part2(std::move(input)) << std::endl;
+  std::cout << "Part 2: " << Part2(input) << std::endl;
 }

2022/CMakeLists.txt

@@ -5,7 +5,7 @@ add_executable(2022_02 02.cpp)
 target_link_libraries(2022_02 aocpp)
 
 add_executable(2022_03 03.cpp)
-target_link_libraries(2022_03 aocpp)
+target_link_libraries(2022_03 aocpp Boost::headers)
 
 add_executable(2022_04 04.cpp)
 target_link_libraries(2022_04 aocpp)