From b523ccb89331b9bebbfcb75c8d428672338fda34 Mon Sep 17 00:00:00 2001 From: Bananymous Date: Fri, 8 Dec 2023 17:13:20 +0200 Subject: [PATCH] AOC2023: Implement day8 Second part was kinda weird. You are supposted to assume something of the input, which necessarily is not true. --- userspace/aoc2023/CMakeLists.txt | 1 + userspace/aoc2023/day8/CMakeLists.txt | 22 +++++ userspace/aoc2023/day8/main.cpp | 131 ++++++++++++++++++++++++++ 3 files changed, 154 insertions(+) create mode 100644 userspace/aoc2023/day8/CMakeLists.txt create mode 100644 userspace/aoc2023/day8/main.cpp diff --git a/userspace/aoc2023/CMakeLists.txt b/userspace/aoc2023/CMakeLists.txt index 1c5f2c67ea..e528db3243 100644 --- a/userspace/aoc2023/CMakeLists.txt +++ b/userspace/aoc2023/CMakeLists.txt @@ -10,6 +10,7 @@ set(AOC2023_PROJECTS day5 day6 day7 + day8 ) set(BANAN_AOC2023_BIN ${BANAN_BIN}/aoc2023) diff --git a/userspace/aoc2023/day8/CMakeLists.txt b/userspace/aoc2023/day8/CMakeLists.txt new file mode 100644 index 0000000000..581feb9e79 --- /dev/null +++ b/userspace/aoc2023/day8/CMakeLists.txt @@ -0,0 +1,22 @@ +cmake_minimum_required(VERSION 3.26) + +project(aoc2023_day8 CXX) + +set(SOURCES + main.cpp +) + +add_executable(aoc2023_day8 ${SOURCES}) +target_compile_options(aoc2023_day8 PUBLIC -O2 -g) +target_link_libraries(aoc2023_day8 PUBLIC libc ban) + +add_dependencies(aoc2023_day8 libc-install ban-install) + +add_custom_target(aoc2023_day8-install + COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day8 ${BANAN_AOC2023_BIN}/day8 + DEPENDS aoc2023_day8 + DEPENDS aoc2023_always +) + +add_dependencies(aoc2023 aoc2023_day8) +add_dependencies(aoc2023-install aoc2023_day8-install) diff --git a/userspace/aoc2023/day8/main.cpp b/userspace/aoc2023/day8/main.cpp new file mode 100644 index 0000000000..4ec0410d2f --- /dev/null +++ b/userspace/aoc2023/day8/main.cpp @@ -0,0 +1,131 @@ +#include +#include + +#include +#include +#include + +using i32 = int32_t; +using i64 = int64_t; + +using u32 = uint32_t; +using u64 = uint64_t; + +static u32 coord_to_u32(BAN::StringView coord) +{ + ASSERT(coord.size() == 3); + return ((u32)coord[2] << 16) | ((u32)coord[1] << 8) | (u32)coord[0]; +} + +i64 puzzle1(FILE* fp) +{ + BAN::HashMap targets; + BAN::String left_right_path; + + { + char buffer[512]; + if (!fgets(buffer, sizeof(buffer), fp)) + return -1; + MUST(left_right_path.append(buffer)); + left_right_path.pop_back(); + + if (!fgets(buffer, sizeof(buffer), fp)) + return -1; + while (fgets(buffer, sizeof(buffer), fp)) + { + BAN::StringView line(buffer); + if (line.size() < 15) + continue; + MUST(targets.emplace( + coord_to_u32(line.substring(0, 3)), + coord_to_u32(line.substring(7, 3)), + coord_to_u32(line.substring(12, 3)) + )); + } + } + + u32 current = coord_to_u32("AAA"sv); + u32 target = coord_to_u32("ZZZ"sv); + + i64 steps = 0; + for (; current != target; steps++) + { + char direction = left_right_path[steps % left_right_path.size()]; + current = targets[current][direction == 'R']; + } + + return steps; +} + +i64 puzzle2(FILE* fp) +{ + BAN::HashMap targets; + BAN::String left_right_path; + + { + char buffer[512]; + if (!fgets(buffer, sizeof(buffer), fp)) + return -1; + MUST(left_right_path.append(buffer)); + left_right_path.pop_back(); + + if (!fgets(buffer, sizeof(buffer), fp)) + return -1; + while (fgets(buffer, sizeof(buffer), fp)) + { + BAN::StringView line(buffer); + if (line.size() < 15) + continue; + MUST(targets.emplace( + coord_to_u32(line.substring(0, 3)), + coord_to_u32(line.substring(7, 3)), + coord_to_u32(line.substring(12, 3)) + )); + } + } + + i64 result = 1; + for (auto [key, _] : targets) + { + if ((key >> 16) != 'A') + continue; + + i64 steps = 0; + for (u32 pos = key; (pos >> 16) != 'Z'; steps++) + { + char direction = left_right_path[steps % left_right_path.size()]; + pos = targets[pos][direction == 'R']; + } + + // Calculating LCM of all steps only works if steps is a multiple of full path size. + // This seems to be the case with my input, but it's good to verify... + ASSERT(steps % left_right_path.size() == 0); + + result = BAN::Math::lcm(result, steps); + } + + return result; +} + +int main(int argc, char** argv) +{ + const char* file_path = "/usr/share/aoc2023/day8_input.txt"; + + if (argc >= 2) + file_path = argv[1]; + + FILE* fp = fopen(file_path, "r"); + if (fp == nullptr) + { + perror("fopen"); + return 1; + } + + printf("puzzle1: %lld\n", puzzle1(fp)); + + fseek(fp, 0, SEEK_SET); + + printf("puzzle2: %lld\n", puzzle2(fp)); + + fclose(fp); +}