AOC2023: Implement day14
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68627995f8
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f46240e879
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@ -16,6 +16,7 @@ set(AOC2023_PROJECTS
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day11
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day12
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day13
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day14
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)
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set(BANAN_AOC2023_BIN ${BANAN_BIN}/aoc2023)
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@ -0,0 +1,22 @@
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cmake_minimum_required(VERSION 3.26)
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project(aoc2023_day14 CXX)
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set(SOURCES
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main.cpp
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)
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add_executable(aoc2023_day14 ${SOURCES})
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target_compile_options(aoc2023_day14 PUBLIC -O2 -g)
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target_link_libraries(aoc2023_day14 PUBLIC libc ban)
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add_dependencies(aoc2023_day14 libc-install ban-install)
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add_custom_target(aoc2023_day14-install
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COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day14 ${BANAN_AOC2023_BIN}/day14
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DEPENDS aoc2023_day14
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DEPENDS aoc2023_always
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)
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add_dependencies(aoc2023 aoc2023_day14)
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add_dependencies(aoc2023-install aoc2023_day14-install)
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@ -0,0 +1,226 @@
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#include <BAN/Array.h>
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#include <BAN/HashMap.h>
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#include <BAN/String.h>
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#include <BAN/Swap.h>
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#include <BAN/Vector.h>
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#include <ctype.h>
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#include <inttypes.h>
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#include <stdio.h>
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using i8 = int8_t;
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using i16 = int16_t;
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using i32 = int32_t;
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using i64 = int64_t;
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using u8 = uint8_t;
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using u16 = uint16_t;
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using u32 = uint32_t;
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using u64 = uint64_t;
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enum class Tile { Empty, RollableRock, StaticRock };
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enum class Direction { North, South, West, East };
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using Platform = BAN::Vector<BAN::Vector<Tile>>;
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Platform parse_platform(FILE* fp)
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{
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Platform platform;
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char buffer[128];
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while (fgets(buffer, sizeof(buffer), fp))
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{
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BAN::StringView line(buffer);
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ASSERT(line.back() == '\n');
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line = line.substring(0, line.size() - 1);
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if (line.empty())
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continue;
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auto char_to_tile =
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[](char c)
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{
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if (c == '.')
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return Tile::Empty;
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if (c == 'O')
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return Tile::RollableRock;
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if (c == '#')
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return Tile::StaticRock;
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ASSERT_NOT_REACHED();
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};
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MUST(platform.emplace_back(line.size()));
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for (size_t i = 0; i < line.size(); i++)
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platform.back()[i] = char_to_tile(line[i]);
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}
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return platform;
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}
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void tilt_platform(Platform& platform, Direction direction)
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{
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switch (direction)
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{
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case Direction::North:
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for (size_t y = 0; y < platform.size(); y++)
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for (size_t x = 0; x < platform.front().size(); x++)
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if (platform[y][x] == Tile::RollableRock)
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for (size_t y_off = 1; y_off <= y && platform[y - y_off][x] == Tile::Empty; y_off++)
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BAN::swap(platform[y - y_off + 1][x], platform[y - y_off][x]);
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break;
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case Direction::West:
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for (size_t x = 0; x < platform.front().size(); x++)
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for (size_t y = 0; y < platform.size(); y++)
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if (platform[y][x] == Tile::RollableRock)
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for (size_t x_off = 1; x_off <= x && platform[y][x - x_off] == Tile::Empty; x_off++)
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BAN::swap(platform[y][x - x_off + 1], platform[y][x - x_off]);
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break;
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case Direction::South:
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for (size_t y = platform.size(); y > 0; y--)
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for (size_t x = 0; x < platform.front().size(); x++)
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if (platform[y - 1][x] == Tile::RollableRock)
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for (size_t y_off = 1; y + y_off - 1 < platform.size() && platform[y + y_off - 1][x] == Tile::Empty; y_off++)
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BAN::swap(platform[y + y_off - 2][x], platform[y + y_off - 1][x]);
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break;
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case Direction::East:
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for (size_t x = platform.front().size(); x > 0; x--)
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for (size_t y = 0; y < platform.size(); y++)
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if (platform[y][x - 1] == Tile::RollableRock)
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for (size_t x_off = 1; x + x_off - 1 < platform.front().size() && platform[y][x + x_off - 1] == Tile::Empty; x_off++)
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BAN::swap(platform[y][x + x_off - 2], platform[y][x + x_off - 1]);
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break;
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default:
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ASSERT_NOT_REACHED();
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}
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}
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i64 puzzle1(FILE* fp)
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{
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auto platform = parse_platform(fp);
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tilt_platform(platform, Direction::North);
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i64 result = 0;
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for (size_t y = 0; y < platform.size(); y++)
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for (size_t x = 0; x < platform.front().size(); x++)
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if (platform[y][x] == Tile::RollableRock)
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result += platform.size() - y;
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return result;
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}
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struct PlatformKey
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{
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BAN::Array<uint64_t, BAN::Math::div_round_up(100 * 100, 64)> data;
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bool operator==(const PlatformKey& other) const
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{
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return memcmp(data.data(), other.data.data(), data.size() * sizeof(decltype(data)::value_type)) == 0;
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}
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};
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struct PlatformKeyHash
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{
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BAN::hash_t operator()(const PlatformKey& key) const
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{
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return key.data.back();
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}
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};
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i64 puzzle2(FILE* fp)
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{
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auto platform = parse_platform(fp);
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ASSERT(platform.size() * platform.front().size() == 100 * 100);
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BAN::HashMap<PlatformKey, size_t, PlatformKeyHash> hit_cache;
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auto build_cache_key =
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[](const Platform& platform) -> PlatformKey
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{
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PlatformKey key;
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for (size_t i = 0; i < 100 * 100; i++)
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{
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const size_t elem = i / 64;
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const size_t bit = i % 64;
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if (platform[i / 100][i % 100] == Tile::RollableRock)
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key.data[elem] |= 1ull << bit;
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}
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return key;
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};
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PlatformKey cycle_begin_key;
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i64 cycle_begin = -1;
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i64 cycle_length = -1;
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i64 missing_cycles = 1'000'000'000;
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for (i64 i = 0; missing_cycles > 0; i++, missing_cycles--)
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{
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auto key = build_cache_key(platform);
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if (cycle_begin == -1)
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{
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if (hit_cache.contains(key))
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{
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cycle_begin = i;
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cycle_begin_key = key;
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}
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else
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{
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MUST(hit_cache.insert(key, i));
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}
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}
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else
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{
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if (key == cycle_begin_key)
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{
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cycle_length = (i - hit_cache[key]) / 2;
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break;
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}
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}
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tilt_platform(platform, Direction::North);
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tilt_platform(platform, Direction::West);
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tilt_platform(platform, Direction::South);
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tilt_platform(platform, Direction::East);
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}
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if (cycle_length != -1)
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missing_cycles %= cycle_length;
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for (; missing_cycles > 0; missing_cycles--)
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{
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tilt_platform(platform, Direction::North);
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tilt_platform(platform, Direction::West);
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tilt_platform(platform, Direction::South);
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tilt_platform(platform, Direction::East);
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}
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i64 result = 0;
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for (size_t y = 0; y < platform.size(); y++)
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for (size_t x = 0; x < platform.front().size(); x++)
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if (platform[y][x] == Tile::RollableRock)
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result += platform.size() - y;
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return result;
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}
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int main(int argc, char** argv)
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{
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const char* file_path = "/usr/share/aoc2023/day14_input.txt";
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if (argc >= 2)
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file_path = argv[1];
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FILE* fp = fopen(file_path, "r");
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if (fp == nullptr)
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{
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perror("fopen");
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return 1;
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}
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printf("puzzle1: %" PRId64 "\n", puzzle1(fp));
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fseek(fp, 0, SEEK_SET);
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printf("puzzle2: %" PRId64 "\n", puzzle2(fp));
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fclose(fp);
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}
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