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#include <filesystem>
#include <fstream>
#include <iostream>
#include <map>
#include <set>
#include <tuple>
using namespace std;
namespace {
using Point = tuple<int, int>;
set<Point>
read_file(const filesystem::path& filename)
{
ifstream file{ filename };
set<Point> points;
int x{};
int y{};
char sep{};
while ( file >> x >> sep >> y ) {
points.insert({ x, y });
}
return points;
}
void
getBoundingBox(const set<Point>& points, Point& topLeft, Point& bottomRight)
{
auto minX = numeric_limits<int>::max();
auto minY = numeric_limits<int>::max();
auto maxX = numeric_limits<int>::min();
auto maxY = numeric_limits<int>::min();
for ( const auto [x, y]: points ) {
minX = min(minX, x);
minY = min(minY, y);
maxX = max(maxX, x);
maxY = max(maxY, y);
}
topLeft = { minX, minY };
bottomRight = { maxX, maxY };
}
int
manhattanDistance(const Point& lhs, const Point& rhs)
{
int distance = abs(get<0>(lhs) - get<0>(rhs)) + abs(get<1>(lhs) - get<1>(rhs));
return distance;
}
void
part1(const set<Point>& points)
{
Point topLeft{};
Point bottomRight{};
getBoundingBox(points, topLeft, bottomRight);
const auto [minX, minY] = topLeft;
const auto [maxX, maxY] = bottomRight;
map<Point, int> areaCount;
set<Point> infinite;
static const int offset = 1;
for ( auto posX = minX - offset; posX <= maxX + offset; ++posX ) {
for ( auto posY = minY - offset; posY <= maxY + offset; ++posY ) {
int bestDistance = numeric_limits<int>::max();
Point bestPoint{};
bool tie = false;
for ( const auto& point: points ) {
int distance = manhattanDistance(point, { posX, posY });
if ( distance < bestDistance ) {
bestDistance = distance;
bestPoint = point;
tie = false;
}
else if ( distance == bestDistance ) {
tie = true;
}
}
if ( !tie ) {
areaCount[bestPoint]++;
if ( posX < minX || posX > maxX || posY < minY || posY > maxY ) {
infinite.insert(bestPoint);
}
}
}
}
int maxSize = 0;
for ( const auto& [point, size]: areaCount ) {
if ( infinite.contains(point) ) {
continue;
}
maxSize = max(maxSize, size);
}
cout << "Part 1: " << maxSize << '\n';
}
void
part2(const set<Point>& points, const int threshold)
{
Point topLeft{};
Point bottomRight{};
getBoundingBox(points, topLeft, bottomRight);
const auto [minX, minY] = topLeft;
const auto [maxX, maxY] = bottomRight;
static const int offset = 100;
unsigned int regionSize = 0;
for ( auto posX = minX - offset; posX <= maxX + offset; ++posX ) {
for ( auto posY = minY - offset; posY <= maxY + offset; ++posY ) {
int sum = 0;
for ( const auto& point: points ) {
int distance = manhattanDistance(point, { posX, posY });
sum += distance;
}
if ( sum < threshold ) {
++regionSize;
}
}
}
cout << "Part 2: " << regionSize << '\n';
}
} // namespace
int
main()
{
auto points = read_file("data/day06.txt");
part1(points);
part2(points, 10000);
}
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