1 files changed, 69 insertions, 0 deletions

diff --git a/day03/solution.cpp b/day03/solution.cpp
new file mode 100644
index 0000000..4ddbe07
--- /dev/null
+++ b/day03/solution.cpp
@@ -0,0 +1,69 @@
+#include <iterator>
+#include <print>
+#include <iostream>
+#include <ranges>
+#include <regex>
+#include <sstream>
+#include <utility>
+#include <vector>
+#include <map>
+#include <unordered_map>
+#include <set>
+#include <unordered_set>
+#include <numeric>
+
+namespace views = std::views;
+namespace ranges = std::ranges;
+
+const auto parse_input() {
+  return std::string(std::istream_iterator<char>(std::cin),
+                     std::istream_iterator<char>());
+}
+
+void part1(const auto &input) {
+  uint64_t answer{0};
+  std::regex re{"mul\\(([0-9]+),([0-9]+)\\)"};
+  const auto begin = std::sregex_iterator(input.begin(), input.end(), re);
+  const auto end = std::sregex_iterator();
+
+  for (auto it = begin; it != end; ++it) {
+      const std::smatch match{*it};
+      answer += std::stoi(match[1].str()) * std::stoi(match[2].str());
+  }
+
+  std::println("{}", answer);
+}
+
+void part2(const auto &input) {
+  uint64_t answer{0};
+  std::regex re{"do\\(\\)|don't\\(\\)|mul\\(([0-9]+),([0-9]+)\\)"};
+  const auto begin = std::sregex_iterator(input.begin(), input.end(), re);
+  const auto end = std::sregex_iterator();
+  bool toggled = true;
+
+  for (auto it = begin; it != end; ++it) {
+    const std::smatch match{*it};
+    if (match.str() == "do()") {
+      toggled = true;
+    } else if (match.str() == "don't()") {
+      toggled = false;
+    } else if (toggled) {
+      answer += std::stoi(match[1].str()) * std::stoi(match[2].str());
+    }
+  }
+
+  std::println("{}", answer);
+}
+
+int main() {
+  const auto input = parse_input();
+
+#ifndef NO_PART1
+  part1(input);
+#endif
+
+#ifndef NO_PART2
+  part2(input);
+#endif
+  return 0;
+}