1 files changed, 197 insertions, 0 deletions

diff --git a/2024/src/day24-alt.cpp b/2024/src/day24-alt.cpp
new file mode 100644
index 0000000..df6d333
--- /dev/null
+++ b/2024/src/day24-alt.cpp
@@ -0,0 +1,197 @@
+#include <array>
+#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;
+}
+
+template<typename Container>
+string
+join(const Container& container, const string& delimiter)
+{
+        ostringstream oss;
+        auto          it = container.begin();
+        if ( it != container.end() ) {
+                oss << *it;
+                ++it;
+        }
+        while ( it != container.end() ) {
+                oss << delimiter << *it;
+                ++it;
+        }
+        return oss.str();
+}
+
+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;
+}
+
+void
+debug(const tuple<map<string, unsigned long>, map<string, tuple<string, string, string>>>& data)
+{
+        const auto& deps = get<1>(data);
+
+        function<void(const string&, size_t)> eval = [&](const string& input, size_t depth) {
+                if ( !deps.contains(input) ) {
+                        return;
+                }
+
+                if ( depth == 3 ) {
+                        return;
+                }
+
+                const auto& [lhs, op, rhs] = deps.at(input);
+
+                const string indent(depth * 2, ' ');
+
+                cout << indent << op << " (" << input << ")\n"
+                     << indent << "  - " << lhs << "\n"
+                     << indent << "  - " << rhs << endl;
+
+                eval(lhs, depth + 1);
+                eval(rhs, depth + 1);
+        };
+
+        eval("z02", 0);
+        eval("z16", 0);
+        eval("z17", 0);
+}
+
+void
+part2(const tuple<map<string, unsigned long>, map<string, tuple<string, string, string>>>& data)
+{
+        auto deps = get<1>(data);
+
+        set<string> wrong;
+        for ( const auto& [res, formula]: deps ) {
+                const auto& [op1, op, op2] = formula;
+
+                if ( res.starts_with('z') && op != "XOR" && res != "z45" ) {
+                        wrong.insert(res);
+                }
+
+                static const set<char> starts{ 'x', 'y', 'z' };
+
+                if ( op == "XOR" && !starts.contains(res[0]) && !starts.contains(op1[0]) && !starts.contains(op2[0]) ) {
+                        wrong.insert(res);
+                }
+
+                if ( op == "AND" && op1 != "x00" && op2 != "x00" ) {
+                        for ( const auto& [subres, subformula]: deps ) {
+                                const auto& [subop1, subop, subop2] = subformula;
+                                if ( (res == subop1 || res == subop2) and subop != "OR" ) {
+                                        wrong.insert(res);
+                                }
+                        }
+                }
+
+                if ( op == "XOR" ) {
+                        for ( const auto& [subres, subformula]: deps ) {
+                                const auto& [subop1, subop, subop2] = subformula;
+                                if ( (res == subop1 || res == subop2) and subop == "OR" ) {
+                                        wrong.insert(res);
+                                }
+                        }
+                }
+        }
+
+        cout << join(wrong, ",") << endl;
+}
+
+int
+main()
+{
+        const auto data = read_file("data/day24.txt");
+        // debug(data);
+        part1(data);
+        part2(data);
+}