2023 Day 5

2023/puzzle-05-01.cc

@@ -0,0 +1,102 @@
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
+#include <iostream>
+#include <iterator>
+#include <string>
+#include <string_view>
+#include <vector>
+
+using UInt = std::uint64_t;
+using NumVec = std::vector<UInt>;
+
+auto operator<<(std::ostream& os, NumVec const& vec) -> std::ostream&
+{
+  for (auto const num : vec) { os << ' ' << num; }
+  return os;
+}
+
+template<typename It>
+void read_nums(It it, std::string_view const nums)
+{
+  char const* pos{nums.data()};
+  while (pos - nums.data() < nums.size()) {
+    char* next_pos{nullptr};
+    *it++ = std::strtoull(pos, &next_pos, 10);
+    pos = next_pos;
+  }
+}
+
+struct MapEntry
+{
+  explicit MapEntry(NumVec const& vec)
+    : dest_(vec[0]), source_(vec[1]), length_(vec[2])
+  {
+    assert(vec.size() == 3);
+  }
+
+  UInt dest_;
+  UInt source_;
+  UInt length_;
+};
+
+struct ThingyMap
+{
+  void add(std::string_view line)
+  {
+    NumVec vec;
+    read_nums(std::back_inserter(vec), line);
+    assert(vec.size() == 3);
+    entries_.emplace_back(vec);
+  }
+
+  [[nodiscard]] auto transform(UInt const in) const -> UInt
+  {
+    for (auto const [dest, source, length] : entries_) {
+      if (in < source) { continue; }
+      if (in >= source + length) { continue; }
+      return dest + (in - source);
+    }
+    return in;
+  }
+
+  std::vector<MapEntry> entries_;
+};
+
+auto main() -> int try {
+  std::string line;
+  NumVec seeds{};
+  std::getline(std::cin, line);
+
+  // Read the seeds.
+  assert(line.substr(0, 6) == "seeds:");
+  read_nums(std::back_inserter(seeds), line.substr(6));
+  std::cout << "Seeds:" << seeds << '\n';
+
+  // Skip whitespace
+  std::getline(std::cin, line);
+
+  while (std::getline(std::cin, line)) {
+    std::cout << line << ":";
+    ThingyMap map;
+    while (std::getline(std::cin, line)) {
+      if (line.empty()) { break; }
+      map.add(line);
+    }
+    NumVec transformed;
+
+    std::transform(seeds.begin(), seeds.end(), std::back_inserter(transformed),
+                   [&map](UInt in) { return map.transform(in); });
+    std::cout << transformed << '\n';
+    seeds = transformed;
+  }
+
+  std::cout << "Minimum: " << *std::ranges::min_element(seeds.begin(), seeds.end()) << '\n';;
+
+  return EXIT_SUCCESS;
+}
+catch (...) {
+  std::cerr << "Uncaught exception.\n";
+  return EXIT_FAILURE;
+}