From a0e775b0a4805a7c1af12c1a956cd9fd74c54b2c Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Tue, 17 Dec 2024 08:39:11 +0100
Subject: Day 17 2024 - this was fun

---
 2024/17/day17b-bruteforce.cpp | 102 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 2024/17/day17b-bruteforce.cpp

(limited to '2024/17/day17b-bruteforce.cpp')

diff --git a/2024/17/day17b-bruteforce.cpp b/2024/17/day17b-bruteforce.cpp
new file mode 100644
index 0000000..a400d5c
--- /dev/null
+++ b/2024/17/day17b-bruteforce.cpp
@@ -0,0 +1,102 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <map>
+#include <queue>
+#include <ranges>
+#include <set>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+class CPU {
+public:
+	CPU(uint64_t a, uint64_t b, uint64_t c) : A{a}, B{b}, C{c} {}
+
+	bool process(const vector<uint64_t>& v) {
+		unsigned j = 0;
+		for (unsigned ip = 0; ip < v.size() && j <= v.size(); ) {
+			switch (v[ip]) {
+			case 0:
+				A >>= combo(v[ip+1]);
+				ip += 2;
+				break;
+			case 1:
+				B ^= v[ip+1];
+				ip += 2;
+				break;
+			case 2:
+				B = combo(v[ip+1]) % 8;
+				ip += 2;
+				break;
+			case 3:
+				ip = A == 0 ? ip+2 : v[ip+1];
+				break;
+			case 4:
+				B ^= C;
+				ip += 2;
+				break;
+			case 5:
+				if (j == v.size() || v[j] != combo(v[ip+1])%8)
+					return false;
+				j++;
+				ip += 2;
+				break;
+			case 6:
+				B = A >> combo(v[ip+1]);
+				ip += 2;
+				break;
+			case 7:
+				C = A >> combo(v[ip+1]);
+				ip += 2;
+				break;
+			default:
+				cout << "Error! Operator " << v[ip] << endl;
+				exit(1);
+			}
+		}
+		return j == v.size();
+	}
+
+	void setreg(uint64_t a, uint64_t b, uint64_t c) {
+		A = a;
+		B = b;
+		C = c;
+	}
+private:
+	uint64_t A, B, C;
+
+	uint64_t& reg(uint64_t i) {
+		return i == 0 ? A : (i == 1 ? B : C);
+	}
+
+	uint64_t combo(uint64_t i) {
+		return i <= 3 ? i : reg(i-4);
+	}
+};
+
+int main() {
+	uint64_t a, b, c;
+	cin >> a >> b >> c;
+	CPU cpu(a, b, c);
+
+	vector<uint64_t> instructions;
+	while (cin >> a)
+		instructions.push_back(a);
+
+	const uint64_t M = 10000000000;
+	const uint64_t N = 100000000000;
+	for (a = M; a < N; a++) {
+if (a % 1000000 == 0)
+cout << "tring " << a << endl;
+		cpu.setreg(a, 0, 0);
+		if (cpu.process(instructions)) {
+			cout << "Found it: " << a << endl;
+			return 0;
+		}
+	}
+	cout << "Not found for A < " << N << endl;
+	return 0;
+}
-- 
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