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#include <fstream>
#include <iostream>
#include <map>
#include <set>
#include <string>
#include <tuple>
using namespace std;
using pos_type = tuple<size_t, size_t>;
map<pos_type, char>
read_file(string_view filename)
{
fstream input{ filename };
map<pos_type, char> data;
size_t yPos = 0;
for ( string line; getline(input, line); ) {
for ( size_t xPos = 0; xPos != line.size(); ++xPos ) {
data[{ xPos, yPos }] = line[xPos];
}
++yPos;
}
return data;
}
void
part1(const map<pos_type, char>& data)
{
map<char, vector<pos_type>> unique_frequencies;
for ( const auto& [position, frequency]: data ) {
if ( frequency == '.' ) {
continue;
}
unique_frequencies[frequency].emplace_back(position);
}
set<pos_type> antinodes;
for ( const auto& [frequency, positions]: unique_frequencies ) {
for ( size_t i = 0; i != positions.size(); ++i ) {
for ( size_t j = i + 1; j != positions.size(); ++j ) {
const auto [lhs_x, lhs_y] = positions[i];
const auto [rhs_x, rhs_y] = positions[j];
const auto delta_x = rhs_x - lhs_x;
const auto delta_y = rhs_y - lhs_y;
pos_type new_position1{ lhs_x - delta_x, lhs_y - delta_y };
if ( data.contains(new_position1) ) {
antinodes.emplace(new_position1);
}
pos_type new_position2{ rhs_x + delta_x, rhs_y + delta_y };
if ( data.contains(new_position2) ) {
antinodes.emplace(new_position2);
}
}
}
}
cout << antinodes.size() << endl;
}
void
part2(const map<pos_type, char>& data)
{
map<char, vector<pos_type>> unique_frequencies;
for ( const auto& [position, frequency]: data ) {
if ( frequency == '.' ) {
continue;
}
unique_frequencies[frequency].emplace_back(position);
}
set<pos_type> antinodes;
for ( const auto& [frequency, positions]: unique_frequencies ) {
for ( size_t i = 0; i != positions.size(); ++i ) {
for ( size_t j = i + 1; j != positions.size(); ++j ) {
const auto [lhs_x, lhs_y] = positions[i];
const auto [rhs_x, rhs_y] = positions[j];
const auto delta_x = rhs_x - lhs_x;
const auto delta_y = rhs_y - lhs_y;
for ( size_t count = 0;; ++count ) {
pos_type new_position{ lhs_x - count * delta_x, lhs_y - count * delta_y };
if ( !data.contains(new_position) ) {
break;
}
antinodes.emplace(new_position);
}
for ( size_t count = 0;; ++count ) {
pos_type new_position{ rhs_x + count * delta_x, rhs_y + count * delta_y };
if ( !data.contains(new_position) ) {
break;
}
antinodes.emplace(new_position);
}
}
}
}
cout << antinodes.size() << endl;
}
int
main()
{
auto data = read_file("data/day08.txt");
part1(data);
part2(data);
}
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