1 files changed, 57 insertions, 0 deletions

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;
+}