day 18, was easy thanks to openscad

d18/draw.awk

@@ -0,0 +1 @@
+{ print "translate([" $1+0.05 "," $2+0.05 "," $3+0.05 "]) cube([0.9,0.9,0.9]);" }

d18/part1.py

@@ -0,0 +1,14 @@
+import sys
+
+S = set()
+for l in sys.stdin.read().splitlines():
+    S.add(tuple(map(int,l.split(','))))
+
+N = 0
+for (x,y,z) in S:
+    n = 6
+    for (i,j,k) in [(0,0,1),(0,0,-1),(0,1,0),(0,-1,0),(1,0,0),(-1,0,0)]:
+        if (x+i,y+j,z+k) in S:
+            n -= 1
+    N += n
+print(N)

d18/part2.py

@@ -0,0 +1,34 @@
+import sys
+
+S = set()  # cubes
+for l in sys.stdin.read().splitlines():
+    S.add(tuple(map(int,l.split(','))))
+
+A = 23
+L = set()  # water
+for x in range(-2,A+1):
+    for y in range(-2,A+1):
+        L.add((x,y,-2))
+more = True
+while more:
+    c = 0
+    for x in range(-2,A+1):
+        for y in range(-2,A+1):
+            for z in range(-2,A+1):
+                if (x,y,z) not in S and (x,y,z) not in L: # water can only expand in air
+                    for (i,j,k) in [(0,0,1),(0,0,-1),(0,1,0),(0,-1,0),(1,0,0),(-1,0,0)]:
+                        if (x+i,y+j,z+k) in L: # if neighbour is water
+                            L.add((x,y,z)) # water expand
+                            c += 1
+                            break
+    more = (c>0)
+
+N = 0
+for (x,y,z) in S:
+    for (i,j,k) in [(0,0,1),(0,0,-1),(0,1,0),(0,-1,0),(1,0,0),(-1,0,0)]:
+        if (x+i,y+j,z+k) in L:
+            N += 1
+print(N)
+
+# > 2489
+# > 2520