From 5a2b9fe23f59757aa9e6d86601a1f8cafdd96865 Mon Sep 17 00:00:00 2001
From: Sebastian Seedorf <mail@sebse.de>
Date: Tue, 15 Dec 2020 21:18:55 +0100
Subject: [PATCH] Day 15 (refactoring)

---
 day15/common.py | 21 +++++++++++++++++++++
 day15/part1.py  | 16 ++--------------
 day15/part2.py  | 16 ++--------------
 3 files changed, 25 insertions(+), 28 deletions(-)
 create mode 100644 day15/common.py

diff --git a/day15/common.py b/day15/common.py
new file mode 100644
index 0000000..a42b0a6
--- /dev/null
+++ b/day15/common.py
@@ -0,0 +1,21 @@
+from functools import reduce
+
+
+def yield_numbers(line: str, target: int):
+    nums = {}
+    turn = 0
+    last_spoken = 0
+    for starting in map(int, line.split(",")):
+        nums[last_spoken] = turn
+        turn += 1
+        last_spoken = starting
+        yield turn, last_spoken
+    for t in range(turn, target):
+        n = t - nums[last_spoken] if last_spoken in nums else 0
+        nums[last_spoken] = t
+        last_spoken = n
+        yield t+1, last_spoken
+
+
+def get_target(line: str, target: int):
+    return reduce(lambda a, b: b, yield_numbers(line, target))
diff --git a/day15/part1.py b/day15/part1.py
index ff94a54..5633b79 100644
--- a/day15/part1.py
+++ b/day15/part1.py
@@ -1,22 +1,10 @@
 #!/usr/bin/env python3
 
-from collections import defaultdict
+from day15.common import get_target
 
 lines = (x.strip() for x in open("input.txt"))
-TARGET = 2020
 
 for line in lines:
     print(line)
-    nums = defaultdict(list)
-    turn = 0
-    last_spoken = 0
-    for starting in map(int, line.split(",")):
-        nums[starting] = [turn]
-        turn += 1
-        last_spoken = starting
-    for t in range(turn, TARGET):
-        last = nums[last_spoken]
-        n = last[1] - last[0] if len(last) == 2 else 0
-        nums[n] = nums[n][-1:] + [t]
-        last_spoken = n
+    last_spoken = get_target(line, 2020)
     print("->", last_spoken)
diff --git a/day15/part2.py b/day15/part2.py
index 1acd8a7..62ec9f3 100644
--- a/day15/part2.py
+++ b/day15/part2.py
@@ -1,22 +1,10 @@
 #!/usr/bin/env python3
 
-from collections import defaultdict
+from day15.common import get_target
 
 lines = (x.strip() for x in open("input.txt"))
-TARGET = 30000000
 
 for line in lines:
     print(line)
-    nums = defaultdict(list)
-    turn = 0
-    last_spoken = 0
-    for starting in map(int, line.split(",")):
-        nums[starting] = [turn]
-        turn += 1
-        last_spoken = starting
-    for t in range(turn, TARGET):
-        last = nums[last_spoken]
-        n = last[1] - last[0] if len(last) == 2 else 0
-        nums[n] = nums[n][-1:] + [t]
-        last_spoken = n
+    last_spoken = get_target(line, 30000000)
     print("->", last_spoken)