aoc 2024, day 24, part 1

1 files changed, 105 insertions, 0 deletions

diff --git a/2024/src/day24.cpp b/2024/src/day24.cpp
new file mode 100644
index 0000000..bf439c7
--- /dev/null
+++ b/2024/src/day24.cpp
@@ -0,0 +1,105 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+using namespace std;
+
+vector<string>
+split(string_view line, string_view delimiter)
+{
+        size_t pos_start = 0;
+        size_t pos_end   = 0;
+
+        vector<string> res;
+
+        while ( (pos_end = line.find(delimiter, pos_start)) != std::string::npos ) {
+                auto token = line.substr(pos_start, pos_end - pos_start);
+                pos_start  = pos_end + delimiter.length();
+
+                res.emplace_back(token);
+        }
+
+        res.emplace_back(line.substr(pos_start));
+        return res;
+}
+
+tuple<map<string, unsigned long>, map<string, tuple<string, string, string>>>
+read_file(string_view filename)
+{
+        fstream    input{ filename };
+        const auto parts = split(string{ istreambuf_iterator<char>{ input }, {} }, "\n\n");
+
+        map<string, unsigned long> inputs;
+
+        // register => { reg1 operator reg2 }
+        map<string, tuple<string, string, string>> deps;
+
+        stringstream spart1{ parts[0] };
+        for ( string line; getline(spart1, line); ) {
+                const auto foo = split(line, ": ");
+                inputs[foo[0]] = stoul(foo[1]);
+        }
+
+        stringstream spart2{ parts[1] };
+        for ( string line; getline(spart2, line); ) {
+                const auto foo = split(line, " ");
+                deps[foo[4]]   = { foo[0], foo[1], foo[2] };
+        }
+
+        return { inputs, deps };
+}
+
+void
+part1(const tuple<map<string, unsigned long>, map<string, tuple<string, string, string>>>& data)
+{
+        auto        inputs = get<0>(data);
+        const auto& deps   = get<1>(data);
+
+        function<unsigned long(const string&)> eval = [&](const string& input) -> unsigned long {
+                if ( inputs.contains(input) ) {
+                        return inputs.at(input);
+                }
+
+                const auto& [lhs, op, rhs] = deps.at(input);
+
+                unsigned long value = 0;
+
+                if ( op == "XOR" ) {
+                        value = eval(lhs) ^ eval(rhs);
+                }
+                else if ( op == "AND" ) {
+                        value = eval(lhs) & eval(rhs);
+                }
+                else if ( op == "OR" ) {
+                        value = eval(lhs) | eval(rhs);
+                }
+                else {
+                        cerr << "Das darf nicht passieren! Input: " << input << endl;
+                }
+
+                inputs[input] = value;
+
+                return value;
+        };
+
+        unsigned long value = 0;
+        for ( const auto& [first, second]: deps ) {
+                if ( first.starts_with("z") ) {
+                        if ( eval(first) != 0 ) {
+                                auto bit = stoul(first.substr(1));
+                                value |= 1UL << bit;
+                        }
+                }
+        }
+        cout << value << endl;
+}
+
+int
+main()
+{
+        const auto data = read_file("data/day24.txt");
+        part1(data);
+}