Poetry stuff.

src/holt59/aoc/2022/day9.py

@@ -0,0 +1,59 @@
+import sys
+
+import numpy as np
+
+
+def move(head: tuple[int, int], command: str) -> tuple[int, int]:
+    h_col, h_row = head
+
+    if command == "L":
+        head = (h_col - 1, h_row)
+    elif command == "R":
+        head = (h_col + 1, h_row)
+    elif command == "U":
+        head = (h_col, h_row + 1)
+    elif command == "D":
+        head = (h_col, h_row - 1)
+
+    return head
+
+
+def follow(head: tuple[int, int], tail: tuple[int, int]) -> tuple[int, int]:
+    h_col, h_row = head
+    t_col, t_row = tail
+
+    if abs(t_col - h_col) <= 1 and abs(t_row - h_row) <= 1:
+        return tail
+
+    return t_col + np.sign(h_col - t_col), t_row + np.sign(h_row - t_row)
+
+
+def run(commands: list[str], n_blocks: int) -> list[tuple[int, int]]:
+    blocks: list[tuple[int, int]] = [(0, 0) for _ in range(n_blocks)]
+    visited = [blocks[-1]]
+
+    for command in commands:
+        blocks[0] = move(blocks[0], command)
+
+        for i in range(0, n_blocks - 1):
+            blocks[i + 1] = follow(blocks[i], blocks[i + 1])
+
+        visited.append(blocks[-1])
+
+    return visited
+
+
+lines = sys.stdin.read().splitlines()
+
+# flatten the commands
+commands: list[str] = []
+for line in lines:
+    d, c = line.split()
+    commands.extend(d * int(c))
+
+
+visited_1 = run(commands, n_blocks=2)
+print(f"answer 1 is {len(set(visited_1))}")
+
+visited_2 = run(commands, n_blocks=10)
+print(f"answer 2 is {len(set(visited_2))}")