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day_22b.cpp
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day_22b.cpp
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#include <algorithm>
#include <cmath>
#include <fstream>
#include <iostream>
#include <numeric>
#include <queue>
#include <stack>
#include <string>
#include <unordered_set>
#include <vector>
#include <regex>
#include <cassert>
struct Brick {
std::array<int, 3> start {0,0,0};
std::array<int, 3> end {0,0,0};
int id = 0;
bool operator == (const Brick& b) const {
return b.start == start && b.end == end;
}
};
bool check_if_overlap(const Brick& b1, const Brick& b2) {
bool x_overlap = false;
bool y_overlap = false;
x_overlap = std::min(b2.start[0], b2.end[0]) <= b1.start[0] && b1.start[0] <= std::max(b2.start[0], b2.end[0]);
y_overlap = std::min(b2.start[1], b2.end[1]) <= b1.start[1] && b1.start[1] <= std::max(b2.start[1], b2.end[1]);
if (x_overlap && y_overlap) return true;
x_overlap = x_overlap || std::min(b2.start[0], b2.end[0]) <= b1.end[0] && b1.end[0] <= std::max(b2.start[0], b2.end[0]);
y_overlap = y_overlap || std::min(b2.start[1], b2.end[1]) <= b1.end[1] && b1.end[1] <= std::max(b2.start[1], b2.end[1]);
if (x_overlap && y_overlap) return true;
x_overlap = x_overlap || std::min(b1.start[0], b1.end[0]) <= b2.start[0] && b2.start[0] <= std::max(b1.start[0], b1.end[0]);
y_overlap = y_overlap || std::min(b1.start[1], b1.end[1]) <= b2.start[1] && b2.start[1] <= std::max(b1.start[1], b1.end[1]);
if (x_overlap && y_overlap) return true;
x_overlap = x_overlap || std::min(b1.start[0], b1.end[0]) <= b2.end[0] && b2.end[0] <= std::max(b1.start[0], b1.end[0]);
y_overlap = y_overlap || std::min(b1.start[1], b1.end[1]) <= b2.end[1] && b2.end[1] <= std::max(b1.start[1], b1.end[1]);
if (x_overlap && y_overlap) return true;
return false;
}
int main(int argc, char * argv[]) {
std::string input = "../input/day_22_input";
if (argc > 1) {
input = argv[1];
}
std::string line;
std::fstream file(input);
const std::regex mask_pattern(R"((-?[0-9]+),(-?[0-9]+),(-?[0-9]+)~(-?[0-9]+),(-?[0-9]+),(-?[0-9]+))");
std::smatch mask_match;
std::vector<Brick> bricks;
while(std::getline(file, line)) {
std::regex_search(line, mask_match, mask_pattern);
Brick b;
b.id = bricks.size();
b.start[0] = std::stoi(mask_match[1]);
b.start[1] = std::stoi(mask_match[2]);
b.start[2] = std::stoi(mask_match[3]);
b.end[0] = std::stoi(mask_match[4]);
b.end[1] = std::stoi(mask_match[5]);
b.end[2] = std::stoi(mask_match[6]);
bricks.push_back(b);
// std::cout << b.start[0] << ' ' << b.start[1] << ' '
// << b.start[2] << ' ' << b.end[0] << ' '
// << b.end[1]<< ' ' << b.end[2] << '\n';
}
for (auto& b : bricks) {
if (b.start[2] > b.end[2]) {
std::swap(b.start, b.end);
}
}
std::sort(
std::begin(bricks),
std::end(bricks),
[](const auto& b1, const auto& b2) {
return b1.start[2] < b2.start[2];
}
);
{
const auto h = bricks[0].end[2] - bricks[0].start[2];
bricks[0].start[2] = 1;
bricks[0].end[2] = 1 + h;
}
for (int i = 1; i < bricks.size(); i++) {
// std::cout << "\nBrick moving down: " << char('A' + bricks[i].id) << '\n';
const auto h = bricks[i].end[2] - bricks[i].start[2];
for (int j = i - 1; j >= 0; j--) {
// std::cout << "Comparing with: " << char('A' + bricks[j].id) << '\n';
bricks[i].start[2] = bricks[j].start[2];
bricks[i].end[2] = bricks[i].start[2] + h;
if (check_if_overlap(bricks[i], bricks[j])) {
// std::cout << "Overlap found between " << char('A' + bricks[i].id) << " and " << char('A' + bricks[j].id) << '\n';
// std::cout << char('A' + bricks[j].id) << " occupies " << bricks[j].start[2] << "->" << bricks[j].end[2] << " in Z" << '\n';
bricks[i].start[2] = bricks[j].end[2] + 1;
bricks[i].end[2] = bricks[i].start[2] + h;
// std::cout << char('A' + bricks[i].id) << " now set to " << bricks[i].start[2] << "->" << bricks[i].end[2] << '\n';
break;
}
}
// While the bricks are arranged in z bfore they start falling,
// they might have a differnt height order after they land
std::partial_sort(
std::begin(bricks),
std::next(std::begin(bricks), i),
std::end(bricks),
[](const auto& b1, const auto& b2) {
return b1.end[2] < b2.end[2];
}
);
}
std::array<int, 3> values {0,0,0};
for (const auto& b : bricks) {
values[0] = std::max(values[0], b.start[0]);
values[0] = std::max(values[0], b.end[0]);
values[1] = std::max(values[1], b.start[1]);
values[1] = std::max(values[1], b.end[1]);
values[2] = std::max(values[2], b.start[2]);
values[2] = std::max(values[2], b.end[2]);
}
std::vector<std::vector<std::vector<int>>> map (
values[0]+1, std::vector<std::vector<int>>(
values[1]+1, std::vector<int>(
values[2]+1, 0
)
)
);
// std::cout << values[0] << ' ' << values[1] << ' ' << values[2] << '\n';
for (const auto& b : bricks) {
for (int x = std::min(b.start[0],b.end[0]); x <= std::max(b.start[0],b.end[0]); x++) {
for (int y = std::min(b.start[1], b.end[1]); y <= std::max(b.start[1],b.end[1]); y++) {
for (int z = std::min(b.start[2], b.end[2]); z <= std::max(b.start[2],b.end[2]); z++) {
// std::cout << x << ' ' << y << ' ' << z << '\n';
map[x][y][z] = b.id;
}
}
}
}
// for (int z = 0; z <= values[2]; z++) {
// for (int x = 0; x <= values[0]; x++) {
// std::cout << map[x][0][z];
// }
// std::cout << '\n';
// }
std::unordered_map<int, std::vector<int>> supports;
std::unordered_map<int, std::vector<int>> supported_by;
for(const auto& b : bricks) {
supports[b.id] = {};
supported_by[b.id] = {};
}
for (int i = 0; i < bricks.size(); i++) {
for (int j = 0; j < bricks.size(); j++) {
if (i == j) continue;
if(bricks[i].end[2] + 1 == bricks[j].start[2] && check_if_overlap(bricks[i], bricks[j])) {
supports[bricks[i].id].push_back(bricks[j].id);
supported_by[bricks[j].id].push_back(bricks[i].id);
}
}
}
std::size_t count = 0;
for (const auto& b : bricks) {
std::queue<int> q;
for (const auto& ele : supports[b.id]) {
q.push(ele);
}
// Do not cache bricks that might have been seen as
// they are added each time one of the bricks that supports them is destroyed
// Only the last time they are added,
// at which point all the bricks supporting them might have been destroyed
// will they be free fall and hence be counted
std::unordered_set<int> moved {b.id};
while(!q.empty()) {
const auto current = q.front();
q.pop();
bool will_move = true;
for (const auto& ele : supported_by[current]) {
if (moved.find(ele) == moved.end()) {
will_move = false;
break;
}
}
if (!will_move) continue;
moved.insert(current);
for (const auto& supported_by_current : supports[current]) {
q.push(supported_by_current);
}
}
count += moved.size() - 1;
}
std::cout << count << '\n';
return 0;
}