forked from Bananymous/banan-os
126 lines
2.4 KiB
C++
126 lines
2.4 KiB
C++
#include <BAN/Array.h>
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#include <BAN/String.h>
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#include <BAN/Vector.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 isize = ssize_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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using usize = size_t;
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template<typename T>
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struct Vec2
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{
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T x, y;
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};
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template<usize W, usize H>
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static BAN::Optional<usize> steps_to_finnish(BAN::Array<BAN::Array<bool, W>, H>& map)
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{
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BAN::Vector<Vec2<usize>> pending;
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MUST(pending.push_back({ 0, 0 }));
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for (usize step = 0;; step++)
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{
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BAN::Vector<Vec2<usize>> next;
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for (auto pos : pending)
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{
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if (map[pos.y][pos.x])
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continue;
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map[pos.y][pos.x] = true;
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if (pos.x == W - 1 && pos.y == H - 1)
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return step;
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if (pos.y > 0 && !map[pos.y - 1][pos.x ]) MUST(next.push_back({ pos.x, pos.y - 1 }));
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if (pos.x > 0 && !map[pos.y ][pos.x - 1]) MUST(next.push_back({ pos.x - 1, pos.y }));
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if (pos.y < H - 1 && !map[pos.y + 1][pos.x ]) MUST(next.push_back({ pos.x, pos.y + 1 }));
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if (pos.x < W - 1 && !map[pos.y ][pos.x + 1]) MUST(next.push_back({ pos.x + 1, pos.y }));
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}
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if (next.empty())
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break;
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pending = BAN::move(next);
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}
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return {};
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}
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i64 part1(FILE* fp)
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{
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BAN::Array<BAN::Array<bool, 71>, 71> map(false);
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for (usize i = 0; i < 1024; i++)
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{
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usize x, y;
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ASSERT(fscanf(fp, "%zu,%zu\n", &x, &y) == 2);
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map[y][x] = true;
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}
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return steps_to_finnish(map).value();
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}
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BAN::String part2(FILE* fp)
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{
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BAN::Vector<Vec2<usize>> bytes;
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for (;;)
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{
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usize x, y;
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if (fscanf(fp, "%zu,%zu\n", &x, &y) != 2)
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break;
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MUST(bytes.push_back({ x, y }));
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}
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usize l = 0;
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usize r = bytes.size() - 1;
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while (l <= r)
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{
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const usize mid = l + (r - l) / 2;
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BAN::Array<BAN::Array<bool, 71>, 71> map(false);
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for (usize i = 0; i <= mid; i++)
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map[bytes[i].y][bytes[i].x] = true;
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if (steps_to_finnish(map).has_value())
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l = mid + 1;
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else if (l == mid)
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return MUST(BAN::String::formatted("{},{}", bytes[mid].x, bytes[mid].y));
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else
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r = mid;
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}
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ASSERT_NOT_REACHED();
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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/aoc2024/day18_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("part1: %" PRId64 "\n", part1(fp));
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fseek(fp, 0, SEEK_SET);
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printf("part2: %s\n", part2(fp).data());
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fclose(fp);
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}
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