banan-os/userspace/aoc2023/day6/main.cpp

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#include <BAN/StringView.h>
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#include <BAN/Vector.h>
#include <ctype.h>
#include <inttypes.h>
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#include <stdio.h>
#include <stdint.h>
using i64 = int64_t;
i64 parse_i64_all_digits(BAN::StringView part)
{
i64 result = 0;
for (char c : part)
if (isdigit(c))
result = (result * 10) + (c - '0');
return result;
}
i64 puzzle1(FILE* fp)
{
BAN::Vector<i64> times, distances;
{
char buffer[128];
fgets(buffer, sizeof(buffer), fp);
BAN::StringView line(buffer);
line = line.substring(10);
line = line.substring(0, line.size() - 1);
auto split = MUST(line.split(' '));
for (auto part : split)
MUST(times.push_back(parse_i64_all_digits(part)));
}
{
char buffer[128];
fgets(buffer, sizeof(buffer), fp);
BAN::StringView line(buffer);
line = line.substring(10);
line = line.substring(0, line.size() - 1);
auto split = MUST(line.split(' '));
for (auto part : split)
MUST(distances.push_back(parse_i64_all_digits(part)));
}
ASSERT(times.size() == distances.size());
i64 result = 1;
for (size_t i = 0; i < times.size(); i++)
{
i64 time = times[i];
i64 distance = distances[i];
i64 min = distance / time - 1;
while ((time - min) * min <= distance)
min++;
i64 max = min;
while ((time - max) * max > distance)
max++;
result *= max - min;
}
return result;
}
i64 puzzle2(FILE* fp)
{
i64 time = 0;
i64 distance = 0;
{
char buffer[128];
fgets(buffer, sizeof(buffer), fp);
BAN::StringView line(buffer);
line = line.substring(10);
time = parse_i64_all_digits(line);
}
{
char buffer[128];
fgets(buffer, sizeof(buffer), fp);
BAN::StringView line(buffer);
line = line.substring(10);
distance = parse_i64_all_digits(line);
}
i64 min = distance / time - 1;
while ((time - min) * min <= distance)
min++;
i64 max = min;
while ((time - max) * max > distance)
max++;
return max - min;
}
int main(int argc, char** argv)
{
const char* file_path = "/usr/share/aoc2023/day6_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));
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fseek(fp, 0, SEEK_SET);
printf("puzzle1: %" PRId64 "\n", puzzle2(fp));
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fclose(fp);
}