Add day 20 solution

day-20/day-20.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+from pathlib import Path
+
+
+def enhance(algorithm, in_image, b):
+    out_image = []
+    for i in range(-b, len(in_image) + b):
+        line = ''
+        for j in range(-b, len(in_image[0]) + b):
+            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\
+                       '#' == in_image[k][l]:
+                        idx += '1'
+                    else:
+                        idx += '0'
+
+            idx = int(idx, 2)
+            line += algorithm[idx]
+        out_image.append(line)
+    return out_image
+
+
+def part_1(input):
+    result = 0
+    algorithm = input[0].rstrip()
+    image = []
+    for line in input[2:]:
+        image.append(line.rstrip())
+    image = enhance(algorithm, image, 3)
+    image = enhance(algorithm, image, -1)
+    for line in image:
+        result += line.count('#')
+
+    print("Part 1 result:", result)
+
+
+def part_2(input):
+    result = 0
+    algorithm = input[0].rstrip()
+    image = []
+    for line in input[2:]:
+        image.append(line.rstrip())
+    for _ in range(25):
+        image = enhance(algorithm, image, 3)
+        image = enhance(algorithm, image, -1)
+    for line in image:
+        result += line.count('#')
+    print("Part 2 result:", result)
+
+
+input = list()
+p = Path(__file__).with_name('input.txt')
+with open(p) as f:
+    input = f.readlines()
+    part_1(input)
+    part_2(input)