2024 day 20

2024/20/main-1.cpp

@@ -0,0 +1,77 @@
+#include "../../include/aoc.hpp"
+#include <bits/stdc++.h>
+using namespace std;
+
+const array<icoord, 4> directions = {
+	icoord(-1, 0),
+	icoord(1, 0),
+	icoord(0, -1),
+	icoord(0, 1),
+};
+
+void rec(icoord c, unordered_map<icoord, int> &m, int score) {
+	if (!m.contains(c)) {
+		return;
+	}
+
+	auto &s = m[c];
+	if (s != -1 && s <= score) {
+		return;
+	}
+
+	s = score;
+	for (auto dir : directions) {
+		rec(c + dir, m, score + 1);
+	}
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string line;
+
+	icoord p, s, e;
+	unordered_map<icoord, int> ms, me;
+	while (getline(cin, line)) {
+		for (p.y = 0; p.y < line.size(); p.y++) {
+			switch (line[p.y]) {
+			case '#':
+				continue;
+			case 'S':
+				s = p;
+				break;
+			case 'E':
+				e = p;
+				break;
+			}
+			ms[p] = -1;
+			me[p] = -1;
+		}
+		p.x++;
+	}
+
+	rec(s, ms, 0);
+	rec(e, me, 0);
+
+	int t = ms[e];
+	int count = 0;
+	for (auto [sc, ss] : ms) {
+		if (ss == -1) {
+			continue;
+		}
+		for (auto [ec, es] : me) {
+			if (es == -1) {
+				continue;
+			}
+			auto dc = sc - ec;
+			if (abs(dc.x) + abs(dc.y) != 2) {
+				continue;
+			}
+			if (ss + es + 2 <= t - 100) {
+				count++;
+			}
+		}
+	}
+	cout << count << '\n';
+}

2024/20/main-2.cpp

@@ -0,0 +1,78 @@
+#include "../../include/aoc.hpp"
+#include <bits/stdc++.h>
+using namespace std;
+
+const array<icoord, 4> directions = {
+	icoord(-1, 0),
+	icoord(1, 0),
+	icoord(0, -1),
+	icoord(0, 1),
+};
+
+void rec(icoord c, unordered_map<icoord, int> &m, int score) {
+	if (!m.contains(c)) {
+		return;
+	}
+
+	auto &s = m[c];
+	if (s != -1 && s <= score) {
+		return;
+	}
+
+	s = score;
+	for (auto dir : directions) {
+		rec(c + dir, m, score + 1);
+	}
+}
+
+int main() {
+	ios::sync_with_stdio(0);
+	cin.tie(0);
+
+	string line;
+
+	icoord p, s, e;
+	unordered_map<icoord, int> ms, me;
+	while (getline(cin, line)) {
+		for (p.y = 0; p.y < line.size(); p.y++) {
+			switch (line[p.y]) {
+			case '#':
+				continue;
+			case 'S':
+				s = p;
+				break;
+			case 'E':
+				e = p;
+				break;
+			}
+			ms[p] = -1;
+			me[p] = -1;
+		}
+		p.x++;
+	}
+
+	rec(s, ms, 0);
+	rec(e, me, 0);
+
+	int t = ms[e];
+	int count = 0;
+	for (auto [sc, ss] : ms) {
+		if (ss == -1) {
+			continue;
+		}
+		for (auto [ec, es] : me) {
+			if (es == -1) {
+				continue;
+			}
+			auto dc = sc - ec;
+			int l = abs(dc.x) + abs(dc.y);
+			if (l > 20) {
+				continue;
+			}
+			if (ss + es + l <= t - 100) {
+				count++;
+			}
+		}
+	}
+	cout << count << '\n';
+}

include/aoc.hpp

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <vector>
+#include <array>
 
 typedef long long ll;
 typedef unsigned long long ull;
@@ -15,6 +15,13 @@ template <typename T> struct Coord {
 		this->y = y;
 	}
 
+	static inline const std::array<Coord<T>, 4> units = {
+		Coord<T>(0, 1),
+		Coord<T>(1, 0),
+		Coord<T>(0, -1),
+		Coord<T>(-1, 0),
+	};
+
 	Coord<T> operator-() { return {-this->x, -this->y}; }
 
 	Coord<T> &operator+=(const Coord<T> &other) {
@@ -40,27 +47,6 @@ template <typename T> struct Coord {
 		y /= other;
 		return *this;
 	}
-
-	std::vector<Coord<T>> nearby(const Coord<T> &cMin, const Coord<T> &cMax) {
-		std::vector<Coord<T>> ret;
-		const T xMin = std::max(this->x - 1, cMin.x);
-		const T xMax = std::min(this->x + 1, cMax.x);
-		const T yMin = std::max(this->y - 1, cMin.y);
-		const T yMax = std::min(this->y + 1, cMax.y);
-		for (T x = xMin; x <= xMax; x++) {
-			for (T y = yMin; y <= yMax; y++) {
-				Coord<T> xy(x, y);
-				if (*this != xy) {
-					ret.push_back(xy);
-				}
-			}
-		}
-		return ret;
-	}
-
-	std::vector<Coord<T>> nearby(const Coord<T> &cMax) {
-		return this->nearby(Coord<T>(), cMax);
-	}
 };
 
 template <typename T>