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#include <cmath>
#include <fstream>
#include <iostream>
#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;
}
vector<string>
expand(const vector<string>& input)
{
vector<string> result;
for ( const auto& line: input ) {
if ( line.find('#') == line.npos ) {
result.emplace_back(line);
}
result.emplace_back(line);
}
for ( size_t col = 0; col != result[0].size(); ++col ) {
bool empty_col = true;
for ( const auto& line: result ) {
if ( line[col] == '#' ) {
empty_col = false;
}
}
if ( empty_col ) {
for ( auto& line: result ) {
line.insert(col, 1, '.');
}
++col;
}
}
return result;
}
vector<tuple<long, long>>
find_points(const vector<string>& input)
{
vector<tuple<long, long>> result;
for ( size_t row = 0; row != input.size(); ++row ) {
const auto& line = input[row];
for ( size_t col = 0; col != line.size(); ++col ) {
if ( line[col] == '#' ) {
result.emplace_back(long(row), long(col));
}
}
}
return result;
}
void
solve(const vector<tuple<long, long>>& points)
{
long sum = 0;
for ( size_t i = 0; i != points.size(); ++i ) {
for ( size_t j = i + 1; j != points.size(); ++j ) {
const auto& from = points[i];
const auto& to = points[j];
sum += abs(get<0>(from) - get<0>(to)) + abs(get<1>(from) - get<1>(to));
}
}
cout << sum << endl;
}
void
part1()
{
solve(find_points(expand(read_file("data/day11.txt"))));
}
void
find_empty_rows_ans_cols(const vector<string>& input, set<long>& cols, set<long>& rows)
{
cols.clear();
rows.clear();
for ( size_t row = 0; row != input.size(); ++row ) {
const auto& line = input[row];
if ( line.find('#') == line.npos ) {
rows.insert(long(row));
}
}
for ( size_t col = 0; col != input[0].size(); ++col ) {
bool empty_col = true;
for ( const auto& line: input ) {
if ( line[col] == '#' ) {
empty_col = false;
}
}
if ( empty_col ) {
cols.insert(long(col));
}
}
}
void
part2()
{
auto input = read_file("data/day11.txt");
auto points = find_points(input);
set<long> cols;
set<long> rows;
find_empty_rows_ans_cols(input, cols, rows);
auto scale = 1000000 - 1;
for ( auto& point: points ) {
const auto row = get<0>(point) + count_if(rows.begin(), rows.end(), [&](long row) { return row < get<0>(point); }) * scale;
const auto col = get<1>(point) + count_if(cols.begin(), cols.end(), [&](long col) { return col < get<1>(point); }) * scale;
point = { row, col };
}
solve(points);
}
int
main()
{
part1();
part2();
}
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