#include <BAN/Array.h> #include <BAN/ScopeGuard.h> #include <BAN/StringView.h> #include <BAN/Vector.h> #include <ctype.h> #include <inttypes.h> #include <stdio.h> using i8 = int8_t; using i16 = int16_t; using i32 = int32_t; using i64 = int64_t; using u8 = uint8_t; using u16 = uint16_t; using u32 = uint32_t; using u64 = uint64_t; BAN::Vector<BAN::Vector<char>> parse_grid(FILE* fp) { BAN::Vector<BAN::Vector<char>> grid; char buffer[256]; while (fgets(buffer, sizeof(buffer), fp)) { BAN::StringView line(buffer); ASSERT(line.back() == '\n'); line = line.substring(0, line.size() - 1); if (line.empty()) break; MUST(grid.emplace_back(line.size(), '\0')); for (size_t i = 0; i < line.size(); i++) grid.back()[i] = line[i]; } return grid; } struct Position { i64 x, y; Position operator+(const Position& other) const { return { .x = x + other.x, .y = y + other.y }; } bool operator==(const Position& other) const { return x == other.x && y == other.y; } }; i64 recurse_grid(BAN::Vector<Position>& path, const BAN::Vector<BAN::Vector<char>>& grid) { const auto entry = path.back(); BAN::ScopeGuard _([&] { while (path.back() != entry) path.pop_back(); }); while (path.back().y < (i64)grid.size() - 1) { BAN::Array<Position, 4> valid_next; size_t valid_next_count = 0; constexpr Position offsets[4] { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } }; for (size_t i = 0; i < 4; i++) { auto next = path.back() + offsets[i]; if (next.y < 0 || next.y >= (i64)grid.size()) continue; if (next.x < 0 || next.x >= (i64)grid.front().size()) continue; switch (grid[next.y][next.x]) { case '^': next.y--; break; case 'v': next.y++; break; case '<': next.x--; break; case '>': next.x++; break; case '#': continue; } if (path.contains(next)) continue; valid_next[valid_next_count++] = next; } if (valid_next_count == 0) return 0; if (valid_next_count == 1) { MUST(path.push_back(valid_next.front())); continue; } i64 result = 0; for (size_t i = 0; i < valid_next_count; i++) { MUST(path.push_back(valid_next[i])); result = BAN::Math::max(result, recurse_grid(path, grid)); path.pop_back(); } return result; } i64 result = 0; for (size_t i = 1; i < path.size(); i++) result += BAN::Math::abs(path[i - 1].x - path[i].x) + BAN::Math::abs(path[i - 1].y - path[i].y); return result; } i64 puzzle1(FILE* fp) { auto grid = parse_grid(fp); BAN::Vector<Position> path; for (i64 x = 0; x < (i64)grid.front().size(); x++) { if (grid.front()[x] == '.') { MUST(path.push_back({ .x = x, .y = 0 })); break; } } return recurse_grid(path, grid); } i64 puzzle2(FILE* fp) { (void)fp; return -1; } int main(int argc, char** argv) { const char* file_path = "/usr/share/aoc2023/day23_input.txt"; if (argc >= 2) file_path = argv[1]; FILE* fp = fopen(file_path, "r"); if (fp == nullptr) { perror("fopen"); return 1; } printf("puzzle1: %" PRId64 "\n", puzzle1(fp)); fseek(fp, 0, SEEK_SET); printf("puzzle2: %" PRId64 "\n", puzzle2(fp)); fclose(fp); }