day22

2 files changed, 110 insertions, 0 deletions

diff --git a/day22 b/day22
new file mode 100644
index 0000000..0ffb865
--- /dev/null
+++ b/day22
@@ -0,0 +1,25 @@
+#.###...#..#..#...##.####
+##.##.#..##.#..#.#..#####
+.####..###.#.#####.#.##.#
+##..#.##.#.#.#...#..##..#
+..#...####.#.###.###...#.
+#..###.##.###.....#....#.
+.#..#.##.##....##...####.
+###.##....#...#.##....##.
+..#.###..######.#.####...
+.#.###..#.##.#..##.######
+###.####.#####.####....#.
+#...####.#.##...##..#.#..
+##.######.#....##.#.####.
+.#.#..#...##....#....#...
+.####.##.#..##...#..####.
+.#.####.##..###..###..##.
+...#...####...#.#.#.###.#
+#.##.####.#..##.###.####.
+.#.#...####....##..####.#
+##.###.##..####..#.######
+#.#...#.#.##.####........
+.......#..##..#.#..###...
+.#..###.###........##.#..
+.######.......#.#.##.#.#.
+.##..#.###.....##.#.#...#
diff --git a/day22.cc b/day22.cc
new file mode 100644
index 0000000..cfe8e59
--- /dev/null
+++ b/day22.cc
@@ -0,0 +1,85 @@
+#include <iostream>
+#include <vector>
+#include <string>
+
+using namespace std;
+
+void
+rotate(int& dy, int &dx)
+{
+	if (dy) {
+		dx = (dy == -1) ? 1 : -1;
+		dy = 0;
+	} else {
+		dy = (dx == -1) ? -1 : 1;
+		dx = 0;
+	}
+}
+
+int
+main() {
+	const int pad = 400;
+	vector<vector<char>> d1;
+
+	string p(pad, '.');
+	for (string line; getline(cin, line); ) {
+		line = p + line + p;
+		d1.emplace_back(begin(line), end(line));
+	}
+	vector<char> padding(2 * pad + size(d1), '.');
+	d1.insert(begin(d1), pad, padding);
+	d1.insert(end(d1), pad, padding);
+
+	vector d2 = d1;
+
+	int p1 = 0, p2 = 0;
+
+	for (int i=0, y=size(d1)/2, x=y, dy=-1, dx=0;
+	     i < 10'000;
+	     i++, y += dy, x += dx) {
+		if (d1[y][x] == '#') { // turn right;
+			rotate(dy, dx);
+		} else { // turn left;
+			rotate(dy, dx);
+			dy = -dy;
+			dx = -dx;
+		}
+
+		if (d1[y][x] == '#') {
+			d1[y][x] = '.';
+		} else {
+			p1++;
+			d1[y][x] = '#';
+		}
+	}
+
+	cout << p1 << endl;   // 5462
+
+	for (int i=0, y=size(d2)/2, x=y, dy=-1, dx=0;
+	     i < 10'000'000;
+	     i++, y += dy, x += dx) {
+		if (d2[y][x] == '#') { // turn right;
+			rotate(dy, dx);
+		} else if (d2[y][x] == '.') { // turn left;
+			rotate(dy, dx);
+			dy = -dy;
+			dx = -dx;
+		} else if (d2[y][x] == 'F') {
+			dy = -dy;
+			dx = -dx;
+		}
+
+		if (d2[y][x] == '#') {
+			d2[y][x] = 'F';
+		} else if (d2[y][x] == '.') {
+			d2[y][x] = 'W';
+		} else if (d2[y][x] == 'W') {
+			p2++;
+			d2[y][x] = '#';
+		} else if (d2[y][x] == 'F') {
+			d2[y][x] = '.';
+		}
+	}
+
+	cout << p2 << endl;   // 2512135
+}