From 77552dcbbb3281246358b24092c4e51156982ac3 Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Fri, 13 Dec 2024 06:51:26 +0100
Subject: Day 13 2024

---
 2024/13/day13b.cpp | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 2024/13/day13b.cpp

(limited to '2024/13/day13b.cpp')

diff --git a/2024/13/day13b.cpp b/2024/13/day13b.cpp
new file mode 100644
index 0000000..b531b7a
--- /dev/null
+++ b/2024/13/day13b.cpp
@@ -0,0 +1,57 @@
+#include <algorithm>
+#include <iostream>
+#include <map>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+#define N 10000000000000
+#define INF 999999
+
+class Machine {
+public:
+	pair<int64_t, int64_t> a, b, p;
+
+	Machine(int64_t a1, int64_t a2,
+	    int64_t b1, int64_t b2, int64_t p1, int64_t p2) :
+	a(a1, a2), b(b1, b2), p(p1, p2) {}
+};
+
+int64_t det(int64_t a, int64_t b, int64_t c, int64_t d) {
+	return a*d - b*c;
+}
+
+pair<int64_t, int64_t> solve_system(const Machine m) {
+	auto d = det(m.a.first, m.b.first, m.a.second, m.b.second);
+	auto dx = det(m.p.first, m.b.first, m.p.second, m.b.second);
+	auto dy = det(m.a.first, m.p.first, m.a.second, m.p.second);
+	return make_pair(dx/d, dy/d);
+}
+
+int main() {
+	string line;
+	int64_t a1, a2, b1, b2, p1, p2;
+	vector <Machine> machines;
+	while (cin >> a1 >> a2) {
+		cin >> b1 >> b2;
+		cin >> p1 >> p2;
+		getline(cin, line);
+		machines.push_back(Machine(a1, a2, b1, b2, p1+N, p2+N));
+	}
+
+	int64_t tot = 0;
+	for (auto m : machines) {
+		auto [x, y] = solve_system(m);
+		if (m.a.first * x + m.b.first * y == m.p.first &&
+		    m.a.second * x + m.b.second * y == m.p.second)
+			tot += 3*x + y;
+	}
+
+	cout << tot << endl;
+
+	return 0;
+}
-- 
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