aoc 2024, day 17, part 1

1 files changed, 110 insertions, 0 deletions

diff --git a/2024/src/day17.cpp b/2024/src/day17.cpp
new file mode 100644
index 0000000..f0d1010
--- /dev/null
+++ b/2024/src/day17.cpp
@@ -0,0 +1,110 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <vector>
+using namespace std;
+
+using program_type   = vector<unsigned long>;
+using registers_type = map<char, unsigned long>;
+
+vector<string>
+split(const string& line, char sep = ' ')
+{
+        vector<string> parts;
+        stringstream   input{ line };
+
+        for ( string part; getline(input, part, sep); ) {
+                parts.emplace_back(part);
+        }
+
+        return parts;
+}
+
+tuple<registers_type, program_type>
+read_file(string_view filename)
+{
+        fstream input{ filename };
+
+        map<char, unsigned long> registers;
+        vector<unsigned long>    program;
+
+        for ( string line; getline(input, line); ) {
+                if ( line.empty() ) {
+                        continue;
+                }
+
+                const auto parts = split(line, ':');
+
+                if ( parts[0] == "Register A" ) {
+                        registers['A'] = stoul(parts[1]);
+                }
+                else if ( parts[0] == "Register B" ) {
+                        registers['B'] = stoul(parts[1]);
+                }
+                else if ( parts[0] == "Register C" ) {
+                        registers['C'] = stoul(parts[1]);
+                }
+                else if ( parts[0] == "Program" ) {
+                        for ( const auto& value: split(parts[1], ',') ) {
+                                program.emplace_back(stoul(value));
+                        }
+                }
+        }
+
+        return { registers, program };
+}
+
+void
+part1(const tuple<registers_type, program_type>& data)
+{
+        auto [registers, program] = data;
+
+        for ( unsigned long ip = 0; ip < program.size(); ) {
+                const auto opcode  = program.at(ip++);
+                const auto operand = program.at(ip++);
+                const auto value   = (operand < 4) ? operand : registers[char('A' + operand - 4)];
+
+                switch ( opcode ) {
+                case 0: // adv
+                        registers['A'] >>= value;
+                        break;
+                case 1: // bxl
+                        registers['B'] ^= operand;
+                        break;
+                case 2: // bst
+                        registers['B'] = value % 8;
+                        break;
+                case 3: // jnz
+                        if ( registers['A'] != 0 ) {
+                                ip = operand;
+                        }
+                        break;
+                case 4:
+                        registers['B'] ^= registers['C'];
+                        break;
+                case 5:
+                        cout << (value & 7) << ',';
+                        break;
+                case 6:
+                        registers['B'] = registers['A'] >> value;
+                        break;
+                case 7:
+                        registers['C'] = registers['A'] >> value;
+                        break;
+                default:
+                        cout << "Error" << endl;
+                        return;
+                }
+        }
+        cout << endl;
+}
+
+int
+main()
+{
+        auto data = read_file("data/day17.txt");
+        part1(data);
+}