Initial set-up for 2019 AoC.

2019/.gitignore

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+cmake-build-*

2019/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.15)
+
+project(aoc2019)
+
+add_library(AoCSolutions src/solutions.hpp src/solutions.cpp src/day01.cpp)
+target_compile_features(AoCSolutions PUBLIC cxx_std_17)
+
+add_executable(runner src/runner.cpp)
+target_compile_features(runner PUBLIC cxx_std_17)
+target_link_libraries(runner AoCSolutions)

2019/src/day01.cpp

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+#include <numeric>
+#include <iterator>
+#include <vector>
+#include <unordered_set>
+#include "solutions.hpp"
+
+// Currently an implementation of 2018 day 1
+void aoc2019::day01_part1(std::istream &input, std::ostream &output) {
+    int sum = std::accumulate(std::istream_iterator<int>(input),
+                              std::istream_iterator<int>(),
+                              0);
+
+    output << sum << std::endl;
+}
+
+void aoc2019::day01_part2(std::istream &input, std::ostream &output) {
+    std::vector<int> drifts;
+    std::copy(std::istream_iterator<int>(input),
+              std::istream_iterator<int>(),
+              std::back_inserter(drifts));
+
+    int cur = 0;
+    std::unordered_set<int> seen{cur};
+    while (true) {
+        for (auto drift : drifts) {
+            cur += drift;
+            if (seen.count(cur) == 1) {
+                output << drift << std::endl;
+                return;
+            } else {
+                seen.insert(cur);
+            }
+        }
+    }
+}

2019/src/runner.cpp

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+#include "solutions.hpp"
+#include <iostream>
+#include <charconv>
+#include <cstring>
+
+template<typename Int, int Radix = 10>
+Int int_from_cstr(Int &value, const char *begin) {
+    const char *end = begin + std::strlen(begin);
+    auto result = std::from_chars(begin, end, value, Radix);
+    if (result.ec != std::errc()) {
+        throw std::invalid_argument("Unparseable integer");
+    }
+
+    return value;
+}
+
+int main(int argc, const char *argv[]) {
+    if (argc < 2) {
+        std::cerr << "Specify a day to run.\n";
+        return 1;
+    }
+
+    int day;
+    int_from_cstr(day, argv[1]);
+
+    const aoc2019::solution_t solution = aoc2019::get_implementation(day);
+    if (solution != nullptr) {
+        solution(std::cin, std::cout);
+        return 0;
+    } else {
+        std::cerr << "Unimplemented.\n";
+        return 1;
+    }
+}

2019/src/solutions.cpp

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+#include <array>
+#include "solutions.hpp"
+
+constexpr const std::array<std::array<aoc2019::solution_t, 2>, 25> SOLUTIONS = {
+        {aoc2019::day01_part1, aoc2019::day01_part2}
+};
+
+aoc2019::solution_t aoc2019::get_implementation(int day, bool part2) {
+    return SOLUTIONS.at(day - 1).at((int) part2);
+}

2019/src/solutions.hpp

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+#pragma once
+
+#include <iosfwd>
+
+namespace aoc2019 {
+    typedef void (*solution_t)(std::istream &, std::ostream &);
+
+    solution_t get_implementation(int day, bool part2 = false);
+
+    // Declarations of all implemented days.
+    void day01_part1(std::istream &input, std::ostream &output);
+    void day01_part2(std::istream &input, std::ostream &output);
+}