1 files changed, 43 insertions, 0 deletions
diff --git a/day16.cc b/day16.cc
new file mode 100644
index 0000000..71851ee
--- /dev/null
+++ b/day16.cc
@@ -0,0 +1,43 @@
+#include <algorithm>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <sstream>
+
+using namespace std;
+
+int
+main() {
+	string d;
+	cin >> d;
+
+	string s(16, ' ');
+	iota(begin(s), end(s), 'a');
+	
+	map<string, int> seen;
+
+        for (int p1 = 0; seen.emplace(s, p1).second; p1++) {
+		char c;
+		istringstream iss{d};
+		while (iss >> c) {
+			if (c == 's') {
+				int r;
+				iss >> r >> c;
+				rotate(begin(s), end(s) - r, end(s));
+			} else if (c == 'x') {
+				int x, y;
+				iss >> x >> c >> y >> c;
+				swap(s[x], s[y]);
+			} else if (c == 'p') {
+				char x, y;
+				iss >> x >> c >> y >> c;
+				swap(s[s.find(x)], s[s.find(y)]);
+			}
+		}
+	}
+
+	for (auto &[k, v] : seen) if (v == 1) cout << k << endl;
+
+	int n = 1'000'000'000UL % size(seen);
+	for (auto &[k, v] : seen) if (v == n) cout << k << endl;
+}