2024 day 6

2024/6/main-1.cpp

@@ -0,0 +1,60 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string line;
+	vector<string> lines;
+	while (getline(cin, line) && !line.empty()) {
+		istringstream l(line);
+		lines.push_back(line);
+	}
+
+	pair<int, int> dir = {-1, 0};
+	pair<int, int> pos;
+	for (int x = 0; x < lines.size(); x++) {
+		for (int y = 0; y < lines[x].size(); y++) {
+			if (lines[x][y] == '^') {
+				pos = {x, y};
+				goto posend;
+			}
+		}
+	}
+posend:;
+
+	int count = 0;
+	while (pos.first >= 0 && pos.first < lines.size() && pos.second >= 0 &&
+		   pos.second < lines[0].size()) {
+		auto x = &lines[pos.first][pos.second];
+		switch (*x) {
+		case '^':
+		case '.':
+			*x = 'X';
+			count++;
+			break;
+		case '#':
+			pos.first -= dir.first;
+			pos.second -= dir.second;
+			switch (dir.first * 2 + dir.second) {
+			case -2:
+				dir = {0, 1};
+				break;
+			case -1:
+				dir = {-1, 0};
+				break;
+			case 1:
+				dir = {1, 0};
+				break;
+			case 2:
+				dir = {0, -1};
+				break;
+			}
+		}
+		pos.first += dir.first;
+		pos.second += dir.second;
+	}
+
+	cout << count << '\n';
+}

2024/6/main-2.cpp

@@ -0,0 +1,74 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string line;
+	vector<string> lines;
+	while (getline(cin, line) && !line.empty()) {
+		istringstream l(line);
+		lines.push_back(line);
+	}
+
+	pair<int, int> pos_;
+	for (int x = 0; x < lines.size(); x++) {
+		for (int y = 0; y < lines[x].size(); y++) {
+			if (lines[x][y] == '^') {
+				pos_ = {x, y};
+				goto posend;
+			}
+		}
+	}
+posend:;
+
+	int count = 0;
+	for (int x = 0; x < lines.size(); x++) {
+		for (int y = 0; y < lines[0].size(); y++) {
+			pair<int, int> dir = {-1, 0};
+			auto pos = pos_;
+			if (lines[x][y] != '.')
+				continue;
+			lines[x][y] = '#';
+
+			map<pair<int, int>, set<int>> track;
+			while (pos.first >= 0 && pos.first < lines.size() &&
+				   pos.second >= 0 && pos.second < lines[0].size()) {
+				if (lines[pos.first][pos.second] == '#') {
+					pos.first -= dir.first;
+					pos.second -= dir.second;
+					int d = dir.first * 2 + dir.second;
+					if (!track.contains(pos)) {
+						set<int> s;
+						track[pos] = s;
+					} else if (track[pos].contains(d)) {
+						count++;
+						goto next;
+					}
+					track[pos].insert(d);
+					switch (d) {
+					case -2:
+						dir = {0, 1};
+						break;
+					case -1:
+						dir = {-1, 0};
+						break;
+					case 1:
+						dir = {1, 0};
+						break;
+					case 2:
+						dir = {0, -1};
+						break;
+					}
+				}
+				pos.first += dir.first;
+				pos.second += dir.second;
+			}
+		next:;
+			lines[x][y] = '.';
+		}
+	}
+
+	cout << count << '\n';
+}