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#include <array>
#include <chrono>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>
using namespace std;
vector<string>
read_file(string_view filename)
{
fstream input{ filename };
vector<string> data;
for ( string line; getline(input, line); ) {
data.emplace_back(line);
}
return data;
}
const unsigned DIR_UP = 0;
const unsigned DIR_RIGHT = 1;
const unsigned DIR_DOWN = 2;
const unsigned DIR_LEFT = 3;
size_t
solve(const vector<string>& lines, tuple<size_t, size_t, unsigned int> start)
{
static const array<tuple<size_t, size_t>, 4> movement{
make_tuple(0, -1),
make_tuple(1, 0),
make_tuple(0, 1),
make_tuple(-1, 0),
};
map<tuple<size_t, size_t, unsigned int>, bool> visited;
queue<tuple<size_t, size_t, unsigned int>> positions;
positions.emplace(start);
while ( !positions.empty() ) {
auto [row, col, dir] = positions.front();
positions.pop();
while ( true ) {
col += get<0>(movement.at(dir % 4));
row += get<1>(movement.at(dir % 4));
if ( row >= lines.size() || col >= lines[0].size() ) {
break;
}
if ( visited[{ row, col, dir }] ) {
break;
}
visited[{ row, col, dir }] = true;
const auto chr = lines[row][col];
if ( (chr == '|' && (dir == DIR_LEFT || dir == DIR_RIGHT)) ||
(chr == '-' && (dir == DIR_UP || dir == DIR_DOWN)) ) {
dir = dir + 1;
positions.emplace(row, col, dir + 2);
}
else if ( (chr == '/' && (dir == DIR_LEFT || dir == DIR_RIGHT)) ||
(chr == '\\' && (dir == DIR_UP || dir == DIR_DOWN)) ) {
dir = dir + 3;
}
else if ( (chr == '\\' && (dir == DIR_LEFT || dir == DIR_RIGHT)) ||
(chr == '/' && (dir == DIR_UP || dir == DIR_DOWN)) ) {
dir = dir + 1;
}
dir %= 4;
}
}
set<tuple<size_t, size_t>> foo;
for ( const auto& bar: visited ) {
foo.emplace(get<0>(bar.first), get<1>(bar.first));
}
return foo.size();
}
void
part1(const vector<string>& lines)
{
auto start = chrono::steady_clock::now();
auto sum = solve(lines, { 0, -1, DIR_RIGHT });
auto duration = chrono::duration_cast<chrono::milliseconds>(chrono::steady_clock::now() - start).count();
cout << sum << " (" << duration << "ms)" << endl;
}
void
part2(const vector<string>& lines)
{
const auto rows = lines.size();
const auto cols = lines[0].size();
auto start = chrono::steady_clock::now();
size_t sum = 0;
for ( size_t row = 0; row != rows; ++row ) {
sum = max(sum, solve(lines, { row, -1, DIR_RIGHT }));
sum = max(sum, solve(lines, { row, cols, DIR_LEFT }));
}
for ( size_t col = 0; col != cols; ++col ) {
sum = max(sum, solve(lines, { -1, col, DIR_DOWN }));
sum = max(sum, solve(lines, { rows, col, DIR_UP }));
}
auto duration = chrono::duration_cast<chrono::milliseconds>(chrono::steady_clock::now() - start).count();
cout << sum << " (" << duration << "ms)" << endl;
}
int
main()
{
const auto lines = read_file("data/day16.txt");
part1(lines);
part2(lines);
}
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