forked from Bananymous/banan-os
133 lines
2.9 KiB
C++
133 lines
2.9 KiB
C++
#include <BAN/StringView.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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#include <string.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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struct Grid2D
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{
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size_t width { 0 };
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size_t height { 0 };
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BAN::Vector<char> data;
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};
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static Grid2D read_grid2d(FILE* fp)
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{
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size_t width { 0 };
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size_t height { 0 };
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BAN::Vector<char> data;
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char buffer[1024];
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while (fgets(buffer, sizeof(buffer), fp))
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{
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const size_t len = strlen(buffer);
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if (len == 0 || buffer[0] == '\n')
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break;
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if (data.empty())
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width = len - 1;
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height++;
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ASSERT(buffer[width] == '\n');
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if (data.capacity() < height * width)
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MUST(data.reserve(2 * height * width));
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MUST(data.resize(height * width));
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memcpy(&data[(height - 1) * width], buffer, width);
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}
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(void)data.shrink_to_fit();
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return Grid2D {
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.width = width,
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.height = height,
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.data = BAN::move(data),
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};
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}
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static bool check_match(const Grid2D& puzzle, size_t x, size_t y, i32 step_x, i32 step_y, BAN::StringView target)
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{
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if (i32 ex = (i32)x + step_x * (i32)(target.size() - 1); ex < 0 || ex >= (i32)puzzle.width)
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return false;
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if (i32 ey = (i32)y + step_y * (i32)(target.size() - 1); ey < 0 || ey >= (i32)puzzle.height)
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return false;
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for (size_t i = 0; i < target.size(); i++)
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if (target[i] != puzzle.data[(y + i * step_y) * puzzle.width + (x + i * step_x)])
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return false;
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return true;
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}
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i64 part1(FILE* fp)
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{
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i64 result = 0;
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auto puzzle = read_grid2d(fp);
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for (size_t y = 0; y < puzzle.height; y++) {
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for (size_t x = 0; x < puzzle.width; x++) {
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result += check_match(puzzle, x, y, 1, 0, "XMAS"_sv);
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result += check_match(puzzle, x, y, 0, 1, "XMAS"_sv);
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result += check_match(puzzle, x, y, 1, 1, "XMAS"_sv);
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result += check_match(puzzle, x, y, 1, -1, "XMAS"_sv);
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result += check_match(puzzle, x, y, 1, 0, "SAMX"_sv);
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result += check_match(puzzle, x, y, 0, 1, "SAMX"_sv);
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result += check_match(puzzle, x, y, 1, 1, "SAMX"_sv);
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result += check_match(puzzle, x, y, 1, -1, "SAMX"_sv);
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}
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}
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return result;
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}
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i64 part2(FILE* fp)
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{
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i64 result = 0;
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auto puzzle = read_grid2d(fp);
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for (size_t y = 1; y < puzzle.height - 1; y++) {
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for (size_t x = 1; x < puzzle.width - 1; x++) {
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if (!check_match(puzzle, x - 1, y - 1, 1, 1, "MAS") && !check_match(puzzle, x - 1, y - 1, 1, 1, "SAM"))
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continue;
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if (!check_match(puzzle, x - 1, y + 1, 1, -1, "MAS") && !check_match(puzzle, x - 1, y + 1, 1, -1, "SAM"))
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continue;
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result++;
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}
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}
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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/aoc2024/day4_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: %" PRId64 "\n", part2(fp));
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fclose(fp);
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}
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