Implement day 2.

2019/src/day02.cpp

@@ -1,10 +1,63 @@
+#include <cstdio>
+#include <exception>
 #include <iostream>
+#include <array>
+#include <vector>
 #include "days.hpp"
 
+static std::vector<int> read_program(std::istream &input) {
+	std::vector<int> program{};
+	for (int current; input >> current; input.ignore()) {
+		program.push_back(current);
+	}
+
+	return program;
+}
+
+static int run_program(std::vector<int> &program) {
+	for (int ip = 0; ip < program.size(); ip += 4) {
+		switch (program[ip]) {
+			case 1:
+				program[program[ip + 3]] = program[program[ip + 1]] + program[program[ip + 2]];
+				break;
+
+			case 2:
+				program[program[ip + 3]] = program[program[ip + 1]] * program[program[ip + 2]];
+				break;
+
+			case 99:
+				return program[0];
+
+			default:
+				char buffer[30];
+				std::snprintf(buffer, sizeof(buffer), "Invalid opcode: %d", program[ip]);
+
+				throw std::domain_error(buffer);
+		}
+	}
+	throw std::out_of_range("Program read out of bounds");
+}
+
 void aoc2019::day02_part1(std::istream &input, std::ostream &output) {
-	output << "Not implemented\n";
+	auto program = read_program(input);
+	program[1] = 12;
+	program[2] = 2;
+	output << run_program(program) << std::endl;
 }
 
 void aoc2019::day02_part2(std::istream &input, std::ostream &output) {
-	output << "Not implemented\n";
+	const auto program = read_program(input);
+
+	for (int noun = 0; noun < 100; ++noun) {
+		for (int verb = 0; verb < 100; ++verb) {
+			auto program_copy = program;
+			program_copy[1] = noun;
+			program_copy[2] = verb;
+			if (run_program(program_copy) == 19690720) {
+				output << 100 * noun + verb << std::endl;
+				return;
+			}
+		}
+	}
+	throw std::domain_error("No valid solution.");
 }