Day 9

9.jl

@@ -0,0 +1,61 @@
+
+const ID = Union{Int,Nothing}
+function getDisk()
+	local blocks::Vector{Int8} = [ x - Int('0') for x in collect(read("input/9")) ][1:end-1]
+	local disk::Vector{ID} = Vector()
+	for b in 1:length(blocks)
+		local id = (b - 1) ÷ 2
+		local size = blocks[b]
+		local isFile = b & 1 == 1
+		for i in 1:size
+			push!(disk, isFile ? id : nothing)
+		end
+	end
+	return disk
+end
+
+const disk = getDisk()
+
+function compress!(arr::AbstractVector, selectRange = (arr, i) -> i:i)
+	for i in reverse(1:length(arr))
+		if !isnothing(arr[i])
+			local fillerRange = selectRange(arr, i)
+			local head = 1
+			while head < i
+				if isnothing(arr[head])
+					local emptyRange = selectRange(arr, head)
+					local l = length(fillerRange)
+					if length(emptyRange) >= l
+						local s = emptyRange[1]
+						arr[s:s+l-1] = arr[fillerRange]
+						arr[fillerRange] .= nothing
+						break
+					else
+						head += l
+						continue
+					end
+				else
+					head += 1
+				end
+			end
+		end
+	end
+	return arr
+end
+
+function selectRangeChunk(arr, i)
+	local c, lower, upper = arr[i], i, i
+	while lower > 1 && arr[lower-1] == c
+		lower -= 1
+	end
+	while upper < length(arr) && arr[upper+1] == c
+		upper += 1
+	end
+	return lower:upper
+end
+
+checksum(arr) = mapreduce(x -> isnothing(x[2]) ? 0 : (x[1]-1) * x[2], +, enumerate(arr))
+
+println("Part one ", checksum(compress!(copy(disk))))
+println("Part two ", checksum(compress!(copy(disk), selectRangeChunk)))
+