add day 19 Python solution

day19/solution.py

@@ -0,0 +1,24 @@
+from collections import defaultdict
+
+with open("input.txt") as f:
+    patterns, designs = f.read().split("\n\n")
+patterns = patterns.split(", ")
+designs = designs.split()
+
+patterns_by_letter = defaultdict(list)
+for pattern in patterns:
+    patterns_by_letter[pattern[0]].append(pattern)
+
+part1 = 0
+part2 = 0
+for design in designs:
+    memo = [1] + [0] * len(design)
+    for i, first_letter in enumerate(design):
+        for pattern in patterns_by_letter[first_letter]:
+            if design.startswith(pattern, i):
+                memo[i + len(pattern)] += memo[i]
+    part1 += memo[-1] > 0
+    part2 += memo[-1]
+
+print("Part 1:", part1)
+print("Part 2:", part2)