6 files changed, 172 insertions, 0 deletions
diff --git a/day06/Dockerfile b/day06/Dockerfile
new file mode 100644
index 0000000..5e0a8b7
--- /dev/null
+++ b/day06/Dockerfile
@@ -0,0 +1,7 @@
+FROM ruby:2.5-slim
+
+WORKDIR /opt
+
+COPY . .
+
+ENTRYPOINT ["./entrypoint"]
diff --git a/day06/Makefile b/day06/Makefile
new file mode 100644
index 0000000..c3e5f10
--- /dev/null
+++ b/day06/Makefile
@@ -0,0 +1,17 @@
+DAY = 06
+
+.PHONY: run clean push
+
+run: build
+	docker run -it --rm aoc2018day$(DAY)
+
+build: part* input
+	docker build -t aoc2018day$(DAY) .
+	touch build
+
+clean:
+	rm -f build
+
+push: build
+	docker tag aoc2018day$(DAY) advent.4574.co.uk/aoc2018day$(DAY)
+	docker push advent.4574.co.uk/aoc2018day$(DAY)
diff --git a/day06/entrypoint b/day06/entrypoint
new file mode 100755
index 0000000..8982d21
--- /dev/null
+++ b/day06/entrypoint
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+if [ -x part1 ] ; then
+	echo -ne "Part 1:\n\t"
+	time ./part1 < input
+fi
+if [ -x part1 -a -x part2 ] ; then
+	echo
+fi
+if [ -x part2 ] ; then
+	echo -ne "Part 2:\n\t"
+	time ./part2 < input
+fi
diff --git a/day06/input b/day06/input
new file mode 100644
index 0000000..8dcb9fa
--- /dev/null
+++ b/day06/input
@@ -0,0 +1,50 @@
+267, 196
+76, 184
+231, 301
+241, 76
+84, 210
+186, 243
+251, 316
+265, 129
+142, 124
+107, 134
+265, 191
+216, 226
+67, 188
+256, 211
+317, 166
+110, 41
+347, 332
+129, 91
+217, 327
+104, 57
+332, 171
+257, 287
+230, 105
+131, 209
+110, 282
+263, 146
+113, 217
+193, 149
+280, 71
+357, 160
+356, 43
+321, 123
+272, 70
+171, 49
+288, 196
+156, 139
+268, 163
+188, 141
+156, 182
+199, 242
+330, 47
+89, 292
+351, 329
+292, 353
+290, 158
+167, 116
+268, 235
+124, 139
+116, 119
+142, 259
diff --git a/day06/part1 b/day06/part1
new file mode 100755
index 0000000..db6ad25
--- /dev/null
+++ b/day06/part1
@@ -0,0 +1,55 @@
+#!/usr/bin/env ruby
+
+def manhattan_distance(x, y, p)
+  return (x - p.first).abs + (y - p.last).abs
+end
+
+def closest_points(x, y, points)
+  dists = points.map{|p|manhattan_distance(x, y, p)}
+  min = dists.min
+  return (0...dists.length).each.select{|i|dists[i] == min}
+end
+
+def edge_points(grid)
+  xa = grid.first
+  xz = grid.last
+  ya = grid.map(&:first).flatten
+  yz = grid.map(&:last).flatten
+  return (xa + xz + ya + yz).compact.uniq
+end
+
+input = $stdin.readlines.map(&:chomp).map{|i|i.split(", ").map(&:to_i)}
+
+xoff = input.map(&:first).min - 1
+yoff = input.map(&:last).min - 1
+
+input.each do |p|
+  p[0] -= xoff
+  p[1] -= yoff
+end
+
+wid = input.map(&:first).max + 1
+hei = input.map(&:last).max + 1
+
+grid = Array.new(wid) { Array.new(hei, nil) }
+
+(0...wid).each do |x|
+  (0...hei).each do |y|
+    cps = closest_points(x, y, input)
+    if cps.length == 1
+      grid[x][y] = cps.first
+    end
+  end
+end
+
+eps = edge_points(grid)
+candidates = (0...input.length).to_a - eps
+
+grid = grid.flatten.compact
+counts = []
+
+candidates.each do |c|
+  counts << grid.count(c)
+end
+
+puts counts.compact.max
diff --git a/day06/part2 b/day06/part2
new file mode 100755
index 0000000..dc74890
--- /dev/null
+++ b/day06/part2
@@ -0,0 +1,30 @@
+#!/usr/bin/env ruby
+
+def manhattan_distance(x, y, p)
+  return (x - p.first).abs + (y - p.last).abs
+end
+
+input = $stdin.readlines.map(&:chomp).map{|i|i.split(", ").map(&:to_i)}
+MAX_DISTANCE = 10000
+
+xoff = input.map(&:first).min - 1
+yoff = input.map(&:last).min - 1
+
+input.each do |p|
+  p[0] -= xoff
+  p[1] -= yoff
+end
+
+wid = input.map(&:first).max + 1
+hei = input.map(&:last).max + 1
+
+grid = Array.new(wid) { Array.new(hei, false) }
+
+(0...wid).each do |x|
+  (0...hei).each do |y|
+    dist_sum = input.map{|p|manhattan_distance(x, y, p)}.sum
+    grid[x][y] = true if dist_sum < MAX_DISTANCE
+  end
+end
+
+puts grid.flatten.count(true)