2024 day 15

2024/15/main-1.cpp

@@ -0,0 +1,82 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+inline void incpair(pair<int, int> &a, pair<int, int> b) {
+	a.first += b.first;
+	a.second += b.second;
+}
+
+inline pair<int, int> addpair(pair<int, int> a, pair<int, int> b) {
+	incpair(a, b);
+	return a;
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	vector<string> grid;
+	string line;
+	set<pair<int, int>> boxes;
+	set<pair<int, int>> walls;
+	pair<int, int> robot;
+	double x = 0;
+	while (getline(cin, line) && !line.empty()) {
+		double y = 0;
+		for (char c : line) {
+			switch (c) {
+			case '#':
+				walls.insert({x, y});
+				break;
+			case 'O':
+				boxes.insert({x, y});
+				break;
+			case '@':
+				robot = {x, y};
+				break;
+			}
+			y++;
+		}
+		x++;
+	}
+
+	while (getline(cin, line) && !line.empty()) {
+		for (char c : line) {
+			pair<int, int> dir;
+			switch (c) {
+			case '<':
+				dir = {0, -1};
+				break;
+			case '>':
+				dir = {0, 1};
+				break;
+			case '^':
+				dir = {-1, 0};
+				break;
+			case 'v':
+				dir = {1, 0};
+				break;
+			}
+
+			auto first = addpair(robot, dir);
+			auto next = first;
+			while (boxes.contains(next)) {
+				incpair(next, dir);
+			}
+			if (walls.contains(next)) {
+				continue;
+			}
+			robot = first;
+			if (boxes.erase(first)) {
+				boxes.insert(next);
+			}
+		}
+	}
+
+	int sum = 0;
+	for (auto box : boxes) {
+		sum += 100 * box.first + box.second;
+	}
+
+	cout << sum << '\n';
+}

2024/15/main-2.cpp

@@ -0,0 +1,117 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+set<pair<int, int>> boxes;
+set<pair<int, int>> walls;
+
+inline void incpair(pair<int, int> &a, pair<int, int> b) {
+	a.first += b.first;
+	a.second += b.second;
+}
+
+inline pair<int, int> addpair(pair<int, int> a, pair<int, int> b) {
+	incpair(a, b);
+	return a;
+}
+
+bool rec(pair<int, int> pos, pair<int, int> dir, set<pair<int, int>> &acc) {
+	if (acc.contains(pos)) {
+		return true;
+	}
+
+	if (walls.contains(pos)) {
+		return false;
+	}
+
+	if (!boxes.contains(pos)) {
+		incpair(pos, {0, -1});
+		if (!boxes.contains(pos)) {
+			return true;
+		}
+	}
+	acc.insert(pos);
+	incpair(pos, dir);
+
+	bool other;
+	switch (dir.second) {
+	case 0:
+		other = rec(addpair(pos, {0, 1}), dir, acc);
+		break;
+	case 1:
+		pos.second += 1;
+	default:
+		other = true;
+	}
+
+	return other && rec(pos, dir, acc);
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	vector<string> grid;
+	string line;
+	pair<int, int> robot;
+	double x = 0;
+	while (getline(cin, line) && !line.empty()) {
+		double y = 0;
+		for (char c : line) {
+			switch (c) {
+			case '#':
+				walls.insert({x, y});
+				walls.insert({x, y + 1});
+				break;
+			case 'O':
+				boxes.insert({x, y});
+				break;
+			case '@':
+				robot = {x, y};
+				break;
+			}
+			y += 2;
+		}
+		x++;
+	}
+
+	while (getline(cin, line) && !line.empty()) {
+		for (char c : line) {
+			pair<int, int> dir;
+			switch (c) {
+			case '<':
+				dir = {0, -1};
+				break;
+			case '>':
+				dir = {0, 1};
+				break;
+			case '^':
+				dir = {-1, 0};
+				break;
+			case 'v':
+				dir = {1, 0};
+				break;
+			}
+
+			set<pair<int, int>> r;
+			auto first = addpair(robot, dir);
+			if (!rec(first, dir, r)) {
+				continue;
+			}
+
+			robot = first;
+			for (auto box : r) {
+				boxes.erase(box);
+			}
+			for (auto box : r) {
+				boxes.insert(addpair(box, dir));
+			}
+		}
+	}
+
+	int sum = 0;
+	for (auto box : boxes) {
+		sum += 100 * box.first + box.second;
+	}
+
+	cout << sum << '\n';
+}