From 500bc234476c313f5ed9db2ce3ddee7b0a852db5 Mon Sep 17 00:00:00 2001
From: Sebastian Seedorf <mail@sebse.de>
Date: Sat, 12 Dec 2020 12:02:09 +0100
Subject: [PATCH] Day 12 (complex numbers)

---
 day12/part1.py | 31 +++++++------------------------
 day12/part2.py | 31 +++++++------------------------
 2 files changed, 14 insertions(+), 48 deletions(-)

diff --git a/day12/part1.py b/day12/part1.py
index c656839..e177190 100644
--- a/day12/part1.py
+++ b/day12/part1.py
@@ -1,34 +1,17 @@
-import numpy as np
-
 lines = ((x[0], int(x[1:].strip())) for x in open("input.txt"))
 
-pos = np.array([0, 0], dtype=np.int32)
-drctn = np.array([1, 0], dtype=np.int32)
-targets = np.array([
-    [0, 1],
-    [1, 0],
-    [0, -1],
-    [-1, 0]
-], dtype=np.int32)
+pos = 0
+drctn = 1
+targets = [1j, 1, -1j, -1]
 target_str = "NESW"
 
-
-def direction(target):
-    return targets[target_str.index(target)]
-
-
-def rotate(current, amount):
-    angle = np.arctan2(current[1], current[0]) + np.pi / 180 * amount
-    amount = np.linalg.norm(current)
-    return np.array([np.rint(np.cos(angle) * amount), np.rint(np.sin(angle) * amount)], dtype=np.int32)
-
-
 for line in lines:
     if line[0] in target_str:
-        pos += direction(line[0]) * line[1]
+        pos += targets[target_str.index(line[0])] * line[1]
     elif line[0] in "LR":
-        drctn = rotate(drctn, -line[1] if line[0] == "R" else line[1])
+        times = (-line[1] if line[0] == "R" else line[1]) / 90
+        drctn = drctn * 1j ** times
     else:
         pos += drctn * line[1]
 
-print(sum(np.abs(pos)))
+print(int(abs(pos.real) + abs(pos.imag)))
diff --git a/day12/part2.py b/day12/part2.py
index d150eca..53a4864 100644
--- a/day12/part2.py
+++ b/day12/part2.py
@@ -1,34 +1,17 @@
-import numpy as np
-
 lines = ((x[0], int(x[1:].strip())) for x in open("input.txt"))
 
-pos = np.array([0, 0], dtype=np.int32)
-drctn = np.array([10, 1], dtype=np.int32)
-targets = np.array([
-    [0, 1],
-    [1, 0],
-    [0, -1],
-    [-1, 0]
-], dtype=np.int32)
+pos = 0
+drctn = 10+1j
+targets = [1j, 1, -1j, -1]
 target_str = "NESW"
 
-
-def direction(target):
-    return targets[target_str.index(target)]
-
-
-def rotate(current, amount):
-    angle = np.arctan2(current[1], current[0]) + np.pi / 180 * amount
-    amount = np.linalg.norm(current)
-    return np.array([np.rint(np.cos(angle) * amount), np.rint(np.sin(angle) * amount)], dtype=np.int32)
-
-
 for line in lines:
     if line[0] in target_str:
-        drctn += direction(line[0]) * line[1]
+        drctn += targets[target_str.index(line[0])] * line[1]
     elif line[0] in "LR":
-        drctn = rotate(drctn, -line[1] if line[0] == "R" else line[1])
+        times = (-line[1] if line[0] == "R" else line[1]) / 90
+        drctn = drctn * 1j ** times
     else:
         pos += drctn * line[1]
 
-print(sum(np.abs(pos)))
+print(int(abs(pos.real) + abs(pos.imag)))