day15

1 files changed, 15 insertions, 0 deletions

diff --git a/day15.rb b/day15.rb
new file mode 100644
index 0000000..f108b61
--- /dev/null
+++ b/day15.rb
@@ -0,0 +1,15 @@
+t = 0
+step = 1
+
+(IO.readlines("day15") << "Disc #7 has 11 positions; at time=0, it is at position 0."
+).each.with_index { |line, i|
+  size, pos = line.scan(/ \d+/).map(&:to_i)
+  
+  while (i+pos+t) % size != 0
+    t += step
+  end
+  
+  step *= size
+}
+
+p t-1