2022 day 9

2022/09/part1

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+
+import math
+
+MOVES = {
+  'U': ( 0, -1),
+  'D': ( 0, +1),
+  'L': (-1,  0),
+  'R': (+1,  0),
+}
+
+TAIL_POSITIONS = set([])
+HEAD = (0, 0)
+TAIL = (0, 0)
+
+def point_add(a, b):
+    return tuple(map(lambda i, j: i + j, a, b))
+
+def move(delta):
+    global TAIL_POSITIONS, HEAD, TAIL
+
+    last_head = HEAD
+    HEAD = point_add(HEAD, delta)
+
+    if ed := math.dist(HEAD, TAIL) < 2.0:
+        _ # do nothing
+    elif ed == 2.0:
+        TAIL = point_add(TAIL, delta)
+    else:
+        TAIL = last_head
+
+    TAIL_POSITIONS.add(TAIL)
+
+with open('input') as f:
+    for line in f:
+        direction, count = line.rstrip().split(" ")
+        for _ in range(int(count)):
+            move(MOVES[direction])
+
+print(len(TAIL_POSITIONS))