1 files changed, 60 insertions, 0 deletions

diff --git a/2024/src/day03.cpp b/2024/src/day03.cpp
new file mode 100644
index 0000000..5b6ec9e
--- /dev/null
+++ b/2024/src/day03.cpp
@@ -0,0 +1,60 @@
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <regex>
+#include <string>
+using namespace std;
+
+string
+read_file(string_view filename)
+{
+        fstream input{ filename };
+        return { istream_iterator<char>{ input }, {} };
+}
+
+void
+part1(const string& data)
+{
+        static const regex pattern(R"(mul\(\d{1,3},\d{1,3}\))");
+
+        long sum = 0;
+        for ( auto it = sregex_iterator(data.begin(), data.end(), pattern); it != sregex_iterator(); ++it ) {
+                long lhs = 0;
+                long rhs = 0;
+                sscanf(it->str().c_str(), "mul(%ld,%ld)", &lhs, &rhs);
+                sum += lhs * rhs;
+        }
+        cout << sum << endl;
+}
+
+void
+part2(const string& data)
+{
+        static const regex pattern(R"(do\(\)|don't\(\)|mul\(\d{1,3},\d{1,3}\))");
+
+        long sum   = 0;
+        bool state = true;
+        for ( auto it = sregex_iterator(data.begin(), data.end(), pattern); it != sregex_iterator(); ++it ) {
+                if ( it->str() == "do()" ) {
+                        state = true;
+                }
+                else if ( it->str() == "don't()" ) {
+                        state = false;
+                }
+                else if ( state ) {
+                        long lhs = 0;
+                        long rhs = 0;
+                        sscanf(it->str().c_str(), "mul(%ld,%ld)", &lhs, &rhs);
+                        sum += lhs * rhs;
+                }
+        }
+        cout << sum << endl;
+}
+
+int
+main()
+{
+        auto data = read_file("data/day03.txt");
+        part1(data);
+        part2(data);
+}