Add day 20

LiquidFun · LiquidFun · commit f8977b2cb119 · 2021-12-22T21:06:22.000+02:00
diff --git a/2021/20/20.jl b/2021/20/20.jl
@@ -1,23 +1,10 @@
-function main()
-    asbin(s) = Int.(collect(s) .== '#') |> join
-    lookup = readline() |> asbin
-    readline()
-    lines = readlines() .|> asbin
-    default = '0'
-    for iteration in 1:50
-        sy, sx = length(lines), length(lines[1])
-        atmap(y, x) = (y ∈ 1:sy && x ∈ 1:sx) ? lines[y][x] : default
-        expanded = []
-        for Y = 0:sy+1
-            push!(expanded, [])
-            for X = 0:sx+1
-                index = parse(Int, join(atmap(Y+y, X+x) for x=-1:1, y=-1:1), base=2)
-                push!(expanded[end], lookup[index + 1])
-            end
-        end
-        lines = expanded
-        default = (default == '0') ? lookup[1] : lookup[end]
-        iteration ∈ [2, 50] && println(lines .|> (line -> line .== '1') |> sum |> sum)
-    end
+lookup, _, lines... = readlines() .|> s -> (Int.(collect(s) .== '#') |> join)
+default = '0'
+for iteration in 1:50
+    sy, sx = length(lines), length(lines[1])
+    atmap(y, x) = (y ∈ 1:sy && x ∈ 1:sx) ? lines[y][x] : default
+    get_index(Y, X) = parse(Int, join(atmap(Y+y, X+x) for x=-1:1, y=-1:1), base=2) + 1
+    global lines = [[lookup[get_index(Y, X)] for X=0:sx+1] for Y=0:sy+1]
+    global default = (default == '0') ? lookup[1] : lookup[end]
+    iteration ∈ [2, 50] && println(lines .|> (line -> line .== '1') |> sum |> sum)
 end
-main()
diff --git a/README.md b/README.md
@@ -1,7 +1,7 @@
 # My Advent of Code Solutions
 
-The solutions are meant to be ran with the `program-tester.sh` script (see [here](https://github.com/LiquidFun/misc-scripts)), which runs the program on all `*.in` files in the directory, and tests whether the corresponding `*.ans` file matches the given output. As of 2021, each program outputs both part 1 and part 2 on separate lines.
+All solutions expect the input via stdin, which can be easily achieved by piping the input to the program: `julia 1.jl < input.in`. I use the `program-tester.sh` script (see [here](https://github.com/LiquidFun/misc-scripts)), which runs the given program on all `*.in` files in the directory, and tests whether the corresponding `*.ans` file matches the given output. Each program outputs both part 1 and part 2 on separate lines. To validate a program manually, type `diff <(julia 1.jl < input.in) input.ans`.
 
 Programs are initialized with the `init-day.sh` script. I.e. typing `init-day.sh 10` initializes the 10th day by creating a folder named `10`, downloading the input test case with the `session.cookie`, copying the `dummy.py` file and opening the solution file.
 
-* 2021: A mix of Julia, Python and APL in that order. Trying out Julia and APL for the first time.
+* 2021: There is a solution for each problem in Julia. Sometimes there is a Python or APL solution as well. I'm trying out Julia for the first time, mostly focusing on short and elegant code. 
