2024 day 12

2024/12/main-1.cpp

@@ -0,0 +1,65 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+vector<vector<tuple<char, bool>>> squares;
+
+bool rec(int x, int y, set<pair<int, int>> &region) {
+	auto &[c, g] = squares[x][y];
+	if (g) {
+		return false;
+	}
+	g = true;
+	region.insert({x, y});
+	vector<pair<int, int>> checks = {
+		{x - 1, y}, {x, y - 1}, {x + 1, y}, {x, y + 1}};
+	for (auto [xx, yy] : checks) {
+		if (xx < 0 || yy < 0 || xx >= squares.size() ||
+			yy >= squares[0].size()) {
+			continue;
+		}
+		if (get<0>(squares[xx][yy]) == c) {
+			rec(xx, yy, region);
+		}
+	}
+	return true;
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string line;
+	while (getline(cin, line) && !line.empty()) {
+		vector<tuple<char, bool>> l;
+		for (char c : line) {
+			l.push_back({c, false});
+		}
+		squares.push_back(l);
+	}
+
+	vector<set<pair<int, int>>> regions;
+	for (int x = 0; x < squares.size(); x++) {
+		for (int y = 0; y < squares[0].size(); y++) {
+			set<pair<int, int>> region;
+			if (rec(x, y, region)) {
+				regions.push_back(region);
+			}
+		}
+	}
+
+	int total = 0;
+	for (auto &region : regions) {
+		int area = region.size();
+		int perim = 0;
+		for (auto [x, y] : region) {
+			for (auto &d : vector<pair<int, int>>(
+					 {{x - 1, y}, {x, y - 1}, {x + 1, y}, {x, y + 1}})) {
+				if (!region.contains(d)) {
+					perim++;
+				}
+			}
+		}
+		total += area * perim;
+	}
+	cout << total << '\n';
+}

2024/12/main-2.cpp

@@ -0,0 +1,78 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+vector<vector<tuple<char, bool>>> squares;
+
+bool rec(int x, int y, set<pair<int, int>> &region) {
+	auto &[c, g] = squares[x][y];
+	if (g) {
+		return false;
+	}
+	g = true;
+	region.insert({x, y});
+	vector<pair<int, int>> checks = {
+		{x - 1, y}, {x, y - 1}, {x + 1, y}, {x, y + 1}};
+	for (auto [xx, yy] : checks) {
+		if (xx < 0 || yy < 0 || xx >= squares.size() ||
+			yy >= squares[0].size()) {
+			continue;
+		}
+		if (get<0>(squares[xx][yy]) == c) {
+			rec(xx, yy, region);
+		}
+	}
+	return true;
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string line;
+	while (getline(cin, line) && !line.empty()) {
+		vector<tuple<char, bool>> l;
+		for (char c : line) {
+			l.push_back({c, false});
+		}
+		squares.push_back(l);
+	}
+
+	vector<set<pair<int, int>>> regions;
+	for (int x = 0; x < squares.size(); x++) {
+		for (int y = 0; y < squares[0].size(); y++) {
+			set<pair<int, int>> region;
+			if (rec(x, y, region)) {
+				regions.push_back(region);
+			}
+		}
+	}
+
+	int total = 0;
+	for (auto &region : regions) {
+		map<pair<int, int>, bool[4]> sides;
+		int area = region.size();
+		for (auto [x, y] : region) {
+			vector<pair<int, int>> directions = {
+				{x - 1, y}, {x + 1, y}, {x, y - 1}, {x, y + 1}};
+			for (int i = 0; i < 4; i++) {
+				sides[{x, y}][i] = !region.contains(directions[i]);
+			}
+		}
+		int sidec = 0;
+		for (auto &[p, b] : sides) {
+			auto [x, y] = p;
+			for (int i = 0; i < 4; i++) {
+				if (!b[i]) {
+					continue;
+				}
+				pair<int, int> other =
+					(i < 2) ? make_pair(x, y - 1) : make_pair(x - 1, y);
+				if (!sides.contains(other) || !sides[other][i]) {
+					sidec++;
+				}
+			}
+		}
+		total += area * sidec;
+	}
+	cout << total << '\n';
+}