133 lines
3.2 KiB
C++
133 lines
3.2 KiB
C++
//
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// Created by Grant Horner on 12/1/25.
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//
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#include <cassert>
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#include <charconv>
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#include <ranges>
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#include <fstream>
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#include <sstream>
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#include "doctest.h"
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enum Direction {
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L = 'L',
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R = 'R',
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};
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struct Instruction {
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Direction direction;
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uint32_t amount;
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};
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Instruction parse_instruction(std::string_view line) {
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assert(!line.empty());
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const auto direction = static_cast<Direction>(line[0]);
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uint32_t amount;
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std::from_chars(&line[1], line.data() + line.size(), amount);
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return Instruction{direction, amount};
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}
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template<>
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struct std::formatter<Instruction> : std::formatter<string_view> {
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static auto format(const Instruction &i, std::format_context &ctx) {
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return std::format_to(ctx.out(), "Instruction[direction: {}, amount: {}]", static_cast<char>(i.direction),
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i.amount);
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}
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};
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const std::string sample =
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"L68\n"
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"L30\n"
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"R48\n"
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"L5\n"
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"R60\n"
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"L55\n"
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"L1\n"
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"L99\n"
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"R14\n"
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"L82\n";
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uint64_t spin2(int &value, Instruction i) {
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uint64_t spins = i.amount / 100;
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int amount_to_spin = i.amount % 100;
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if (i.direction == L) {
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amount_to_spin *= -1;
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}
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value += amount_to_spin;
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if (value == 0) {
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spins++;
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} else if (value < 0) {
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spins++;
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value = 100 + value;
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} else if (100 < value) {
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spins++;
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value = value - 100;
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}
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return spins;
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}
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bool spin(int &value, Instruction i) {
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value += static_cast<int>(i.amount) * (i.direction == L ? -1 : 1);
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value %= 100;
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return value == 0;
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}
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uint32_t solve_first(const std::string &input) {
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int value = 50;
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uint32_t spins = 0;
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for (const auto instr:
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std::views::split(input, '\n')
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| std::views::transform([](auto s) { return std::string_view(s); })
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| std::views::filter([](const std::string_view s) { return !s.empty(); })
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| std::views::transform(parse_instruction)
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) {
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if (spin(value, instr)) {
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spins++;
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}
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// std::println("Total spins: {}, instruction: {}, value: {}", spins, instr, value);
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}
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return spins;
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}
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TEST_SUITE_BEGIN("Day 1");
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TEST_CASE("puzzle 1") {
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CHECK(solve_first(sample) == 3);
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std::ifstream input("day1input.txt");
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CHECK(input.is_open());
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std::stringstream buffer;
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buffer << input.rdbuf();
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CHECK(solve_first(buffer.str()) == 1158);
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}
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uint32_t solve_second(const std::string &input) {
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int value = 50;
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uint32_t spins = 0;
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for (const auto instr:
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std::views::split(input, '\n')
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| std::views::transform([](auto s) { return std::string_view(s); })
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| std::views::filter([](const std::string_view s) { return !s.empty(); })
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| std::views::transform(parse_instruction)
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) {
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spins += spin2(value, instr);
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// std::println("Total spins: {}, instruction: {}, value: {}", spins, instr, value);
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}
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return spins;
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}
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TEST_CASE("puzzle 2") {
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CHECK(solve_second(sample) == 6);
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std::ifstream input("day1input.txt");
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CHECK(input.is_open());
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std::stringstream buffer;
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buffer << input.rdbuf();
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CHECK(solve_second(buffer.str()) == 6860);
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}
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TEST_SUITE_END();
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