From ae1e96f10b399266825e275ca4a8100ceede9cad Mon Sep 17 00:00:00 2001
From: Thomas Schmucker <ts@its1.de>
Date: Thu, 23 Oct 2025 19:28:20 +0200
Subject: days 19-25, aoc 2016

---
 2016/src/day19.cpp | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 2016/src/day19.cpp

(limited to '2016/src/day19.cpp')

diff --git a/2016/src/day19.cpp b/2016/src/day19.cpp
new file mode 100644
index 0000000..2d7282f
--- /dev/null
+++ b/2016/src/day19.cpp
@@ -0,0 +1,45 @@
+#include <cmath>
+#include <iostream>
+
+using namespace std;
+
+namespace {
+
+template<typename T>
+T
+fn(T N)
+    requires std::is_integral_v<T>
+{
+	return T(1) << static_cast<T>(floor(log2(N)));
+}
+
+void
+part1(unsigned N)
+{
+	cout << (2 * (N - fn(N))) + 1 << '\n';
+}
+
+void
+part2(unsigned N)
+{
+	auto log_3 = [](double x) { return log(x) / log(3); };
+
+	auto threes = pow(3, floor(log_3(N - 1)));
+	if ( N <= 2 * threes ) {
+		cout << static_cast<unsigned>(N - threes);
+	}
+	else {
+		cout << static_cast<unsigned>(N - threes + N - (2 * threes));
+	}
+	cout << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+	const unsigned puzzle = 3017957;
+	part1(puzzle);
+	part2(puzzle);
+}
-- 
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