9-2

9/twostar.py

@@ -0,0 +1,44 @@
+seen = set()
+front = (0,0)
+tail = (0,0)
+
+snek = [(0,0) for _ in range(10)]
+
+direction = {
+    "R": (1, 0),
+    "L": (-1, 0),
+    "U": (0, 1),
+    "D": (0, -1)
+}
+
+def move(back, front):
+    new = (0, 0)
+    if back[0] == front[0] and abs(back[1] - front[1]) > 1:
+        # Vertical move
+        new = (back[0], int((back[1] + front[1]) / 2))
+    elif back[1] == front[1] and abs(back[0] - front[0]) > 1:
+        new = (int((back[0] + front[0]) / 2), back[1])
+    elif abs(back[0] - front[0]) <= 1 and abs(back[1] - front[1]) <= 1:
+        # Touching diagonal, no action required
+        new = back
+    else: 
+        # Non-touching diagonal, step required
+        dir = (min(1, max(-1, front[0] - back[0])), min(1, max(-1, front[1] - back[1])))
+        new = (back[0] + dir[0], back[1] + dir[1])
+    return new
+
+def moveSnek():
+    for i in range(1, 10):
+        snek[i] = move(snek[i], snek[i-1])
+
+
+with open("input.txt", "r") as f:
+    seen.add(snek[9])
+    for line in f.readlines():
+        line = line.strip()
+        [dir, steps] = line.split(" ")
+        for _ in range(int(steps)):
+            snek[0] = (snek[0][0] + direction[dir][0], snek[0][1] + direction[dir][1])
+            moveSnek()
+            seen.add(snek[9])
+print(len(seen))