days 19-25, aoc 2016

1 files changed, 45 insertions, 0 deletions

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);
+}