From 1bf812ce9db606f43ca4ffcdb10700c70faa71dd Mon Sep 17 00:00:00 2001
From: Patrick Michl <patrick.michl@hetzner.com>
Date: Thu, 9 Dec 2021 07:22:03 +0100
Subject: [PATCH] solve and cleanup day9

---
 src/day_9.jl | 88 +++++++++++++++++-----------------------------------
 1 file changed, 29 insertions(+), 59 deletions(-)

diff --git a/src/day_9.jl b/src/day_9.jl
index 1a17115..cb76b8f 100644
--- a/src/day_9.jl
+++ b/src/day_9.jl
@@ -4,87 +4,57 @@ using Pipe: @pipe
 using Combinatorics
 
 
-function p1(input::Vector{String})
-	map = []
-	for l in input
-		push!(map, [ parse(Int, c) for c in l ])
-	end
-	risks = 0
-	for x in 1:length(map)
-		for y in 1:length(map[1])
-			adjacent = []
-			for (a,b) in [[0,1], [1,0], [0,-1], [-1,0]]
-				i = x + a
-				j = y + b
-
-				if i < 1 || i > length(map) || j < 1 || j > length(map[1])
-					continue
-				end
-				push!(adjacent, map[i][j])
-			end
-			@info map[x][y]
-			@info adjacent
-			if map[x][y] < minimum(adjacent)
-				@info "low"
-				risks += map[x][y] + 1
-			end
-		end
-	end
-	return risks
-end
-
 function lowpoints(map)
-	low = []
+	low = Dict()
 	for x in 1:length(map)
 		for y in 1:length(map[1])
 			adjacent = []
-			for (a,b) in [[0,1], [1,0], [0,-1], [-1,0]]
-				i = x + a
-				j = y + b
-
-				if i < 1 || i > length(map) || j < 1 || j > length(map[1])
-					continue
+			for (i,j) in [ [x+i,y+j] for (i,j) in zip([0,1,0,-1], [1,0,-1,0]) ]
+				if i in 1:length(map) && j in 1:length(map[1])
+					push!(adjacent, map[i][j])
 				end
-				push!(adjacent, map[i][j])
 			end
 			if map[x][y] < minimum(adjacent)
-				push!(low, [x,y])
+				low[[x,y]] = map[x][y]
 			end
 		end
 	end
 	return low
 end
 
-function search(map, pos)
-	queue = [pos]
-	visited = [pos]
+function p1(input::Vector{String})
+	map = [ parse.(Int, collect(l)) for l in input ]
+	low = lowpoints(map)
+	return sum(values(low)) + length(low)
+end
 
-	while length(queue) > 0
-		c = popfirst!(queue)
-		h = map[c[1], c[2]]
-		for pos in [ [x+i,y+j] for (i,j) in zip([0,1,0,-1], [1,0,-1,0]) ]
-			if p[1] < 1 || p[1] > length(map) || p[2] < 1 || p[2] > length(map[1])
-				continue
-			end
-			if pos ∉ visited
-				h2 = map[p[1]][p[2]]
-				if h2 < 9 && h2 > h
-					push!(visited, pos)
-					push!(queue, pos)
+
+function search(map, pos)
+	q = [pos]
+	v = [pos]
+
+	while length(q) > 0
+		c = popfirst!(q)
+		h = map[c[1]][c[2]]
+		for p in [ [c[1]+i,c[2]+j] for (i,j) in zip([0,1,0,-1], [1,0,-1,0]) ]
+			if p[1] in 1:length(map) && p[2] in 1:length(map[1])
+				if p ∉ v
+					h2 = map[p[1]][p[2]]
+					if h < h2 < 9
+						push!(v, p)
+						push!(q, p)
+					end
 				end
 			end
 		end
 	end
-	return visited
+	return v
 end
 
 function p2(input::Vector{String})
-	map = []
-	for l in input
-		push!(map, [ parse(Int, c) for c in l ])
-	end
+	map = [ parse.(Int, collect(l)) for l in input ]
 	low = lowpoints(map)
-	basin_sizes = [ length(search(map, p)) for p in low ]
+	basin_sizes = [ length(search(map, p)) for p in keys(low) ]
 	return prod(sort(basin_sizes)[end-2:end])
 end