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#include <filesystem>
#include <fstream>
#include <iostream>
#include <map>
#include <string>
#include <tuple>
using namespace std;
namespace {
using dir_type = tuple<size_t, size_t>;
using pos_type = tuple<size_t, size_t>;
using puzzle_type = map<pos_type, char>;
puzzle_type
read_file(const filesystem::path& filename)
{
ifstream file{ filename };
puzzle_type data;
size_t row = 0;
for ( string line; getline(file, line); ) {
for ( size_t col = 0; col != line.size(); ++col ) {
if ( line.at(col) != ' ' ) {
data.emplace(pos_type{ col, row }, line.at(col));
}
}
++row;
}
return data;
}
pos_type
find_start(const puzzle_type& puzzle)
{
for ( size_t col = 0;; ++col ) {
const pos_type pos{ col, 0 };
if ( puzzle.contains(pos) && puzzle.at(pos) == '|' ) {
return pos;
}
}
}
void
solve(const puzzle_type& puzzle)
{
string result;
size_t steps = 0;
pos_type pos = find_start(puzzle);
dir_type dir{ 0, 1 };
while ( puzzle.contains(pos) ) {
auto chr = puzzle.at(pos);
if ( chr >= 'A' && chr <= 'Z' ) {
result += chr;
}
else if ( chr == '+' ) {
auto [dx, dy] = dir;
auto left = dir_type{ -dy, dx };
auto right = dir_type{ dy, -dx };
pos_type next_left = { get<0>(pos) + get<0>(left), get<1>(pos) + get<1>(left) };
pos_type next_right = { get<0>(pos) + get<0>(right), get<1>(pos) + get<1>(right) };
if ( puzzle.contains(next_left) ) {
dir = left;
}
else if ( puzzle.contains(next_right) ) {
dir = right;
}
else {
cerr << "Error!\n";
return;
}
}
get<0>(pos) += get<0>(dir);
get<1>(pos) += get<1>(dir);
++steps;
}
cout << "Part1: " << result << '\n';
cout << "Part2: " << steps << '\n';
}
} // namespace
int
main()
{
auto puzzle = read_file("data/day19.txt");
solve(puzzle);
}
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