Update day 20 solution

day-20/day-20.py

@@ -2,24 +2,29 @@
 from pathlib import Path
 
 
-def enhance(algorithm, in_image, b):
+def enhance(algorithm, in_image, boundary):
     out_image = []
-    for i in range(-b, len(in_image) + b):
+    height = len(in_image)
+    width = len(in_image[0])
+    for i in range(-boundary, height + boundary):
         line = ''
-        for j in range(-b, len(in_image[0]) + b):
+        valid = False
+        for j in range(-boundary, width + boundary):
             idx = ''
             for k in range(i - 1, i + 2):
                 for l in range(j - 1, j + 2):
-                    if 0 <= k < len(in_image) and \
-                       0 <= l < len(in_image[k]) and\
+                    if 0 <= k < height and \
+                       0 <= l < width and \
                        '#' == in_image[k][l]:
                         idx += '1'
                     else:
                         idx += '0'
-
             idx = int(idx, 2)
+            if not valid and '#' == algorithm[idx]:
+                valid = True
             line += algorithm[idx]
-        out_image.append(line)
+        if valid:
+            out_image.append(line)
     return out_image