2024 day 16

2024/16/main-1.cpp

@@ -0,0 +1,71 @@
+#include <bits/stdc++.h>
+#include "../../include/aoc.hpp"
+using namespace std;
+
+unordered_map<Coord<int>, unordered_map<int, int>> m;
+
+inline Coord<int> posdir(int p) {
+	switch (p) {
+	case 0:
+		return {0, 1};
+	case 1:
+		return {1, 0};
+	case 2:
+		return {0, -1};
+	case 3:
+		return {-1, 0};
+	default:
+		return {};
+	}
+}
+
+void rec(Coord<int> pos, int dir, int score) {
+	if (!m.contains(pos)) {
+		return;
+	}
+
+	auto &mp = m[pos];
+	if (mp.contains(dir) && mp[dir] <= score) {
+		return;
+	}
+
+	mp[dir] = score;
+	rec(pos + posdir(dir), dir, score + 1);
+	rec(pos, (dir + 1) & 3, score + 1000);
+	rec(pos, (dir - 1) & 3, score + 1000);
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	Coord<int> pos, s, e;
+	string line;
+	while (getline(cin, line) && !line.empty()) {
+		for (pos.y = 0; pos.y < line.size(); pos.y++) {
+			switch (line[pos.y]) {
+			case '#':
+				continue;
+			case 'S':
+				s = pos;
+				break;
+			case 'E':
+				e = pos;
+				break;
+			}
+			m[pos];
+		}
+		pos.x++;
+	}
+
+	rec(s, 0, 0);
+
+	int minscore = -1;
+	for (auto [dir, score] : m[e]) {
+		if (minscore == -1 || score < minscore) {
+			minscore = score;
+		}
+	}
+
+	cout << minscore << '\n';
+}

2024/16/main-2.cpp

@@ -0,0 +1,111 @@
+#include <bits/stdc++.h>
+#include "../../include/aoc.hpp"
+using namespace std;
+
+unordered_map<Coord<int>, unordered_map<int, pair<int, set<int>>>> m;
+
+inline Coord<int> posdir(int p) {
+	switch (p) {
+	case 0:
+		return {0, 1};
+	case 1:
+		return {1, 0};
+	case 2:
+		return {0, -1};
+	case 3:
+		return {-1, 0};
+	default:
+		return {};
+	}
+}
+
+void rec(Coord<int> pos, int dir, int score, int follow) {
+	if (!m.contains(pos)) {
+		return;
+	}
+
+	auto &mp = m[pos];
+
+	if (mp.contains(dir)) {
+		auto &[s, f] = mp[dir];
+		if (s < score) {
+			return;
+		}
+
+		if (s > score) {
+			f.clear();
+		}
+		f.insert(follow);
+		if (s == score) {
+			return;
+		}
+
+		s = score;
+	} else {
+		mp[dir] = {score, {follow}};
+	}
+
+	mp[dir].second.insert(follow);
+
+	rec(pos + posdir(dir), dir, score + 1, dir);
+	rec(pos, (dir + 1) & 3, score + 1000, follow);
+	rec(pos, (dir - 1) & 3, score + 1000, follow);
+}
+
+void rec2(unordered_set<Coord<int>> &mm, Coord<int> pos, int dir) {
+	mm.insert(pos);
+	auto &[s, f] = m[pos][dir];
+	for (auto follow : f) {
+		if (follow == -1) {
+			continue;
+		}
+
+		rec2(mm, pos + posdir((follow + 2) & 3), follow);
+	}
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	Coord<int> pos, s, e;
+	string line;
+	while (getline(cin, line) && !line.empty()) {
+		for (pos.y = 0; pos.y < line.size(); pos.y++) {
+			switch (line[pos.y]) {
+			case '#':
+				continue;
+			case 'S':
+				s = pos;
+				break;
+			case 'E':
+				e = pos;
+				break;
+			}
+			m[pos];
+		}
+		pos.x++;
+	}
+
+	rec(s, 0, 0, -1);
+
+	int minscore = -1;
+	vector<int> dirs;
+	for (auto &[dir, sf] : m[e]) {
+		auto &[s, f] = sf;
+		if (minscore == -1 || s < minscore) {
+			minscore = s;
+			dirs.clear();
+		} else if (s > minscore) {
+			continue;
+		}
+		dirs.push_back(dir);
+	}
+
+	unordered_set<Coord<int>> mm;
+	for (auto dir : dirs) {
+		rec2(mm, e, dir);
+	}
+
+	cout << mm.size() << '\n';
+}