132 lines
2.4 KiB
C++
132 lines
2.4 KiB
C++
#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 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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static BAN::Vector<BAN::String> parse_lines(FILE* fp)
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{
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BAN::Vector<BAN::String> lines;
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MUST(lines.emplace_back());
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char line_buffer[128];
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while (fgets(line_buffer, sizeof(line_buffer), fp))
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{
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MUST(lines.back().append(line_buffer));
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if (lines.back().back() != '\n')
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continue;
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lines.back().pop_back();
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MUST(lines.emplace_back());
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}
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while (lines.back().empty())
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lines.pop_back();
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return lines;
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}
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i64 part1(FILE* fp)
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{
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i32 result = 0;
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auto lines = parse_lines(fp);
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for (char& ch : lines.front())
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if (ch == 'S')
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ch = '|';
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for (size_t y = 0; y < lines.size() - 1; y++)
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{
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for (size_t x = 0; x < lines[y].size(); x++)
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{
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if (lines[y][x] != '|')
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continue;
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switch (lines[y + 1][x])
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{
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case '.':
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lines[y + 1][x] = '|';
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break;
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case '^':
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lines[y + 1][x - 1] = '|';
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lines[y + 1][x + 1] = '|';
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result++;
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break;
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}
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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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auto lines = parse_lines(fp);
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const size_t h = lines.size();
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const size_t w = lines.front().size();
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BAN::Vector<i64> timelines;
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MUST(timelines.resize(w * h));
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const auto get_char_value = [](char ch) { return ch == '.' ? 0 : ch == 'S' ? 1 : -1; };
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for (size_t y = 0; y < h; y++)
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for (size_t x = 0; x < w; x++)
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timelines[y * w + x] = get_char_value(lines[y][x]);
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for (size_t y = 1; y < h; y++)
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{
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for (size_t x = 0; x < w; x++)
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{
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if (timelines[(y - 1) * w + x] < 0)
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;
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else if (timelines[y * w + x] >= 0)
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timelines[y * w + x] += timelines[(y - 1) * w + x];
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else
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{
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timelines[y * w + x - 1] += timelines[(y - 1) * w + x];
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timelines[y * w + x + 1] += timelines[(y - 1) * w + x];
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}
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}
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}
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i64 result = 0;
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for (size_t x = 0; x < w; x++)
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if (auto value = timelines[(h - 1) * w + x]; value > 0)
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result += value;
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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/aoc2025/day7_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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