Added part-a of Day 9

2022/q09a.py

@@ -0,0 +1,44 @@
+from aocd.models import Puzzle
+puzzle = Puzzle(year=2022, day=9)
+
+rope_length = 2
+rope = [[0, 0] for _ in range(rope_length)]
+visited = set()
+visited.add(tuple(rope[-1]))
+UNIT_VECTORS = { 'L': (0, -1), 'R': (0, 1), 'U': (1, 1), 'D': (1, -1) }
+
+def make_move(direction, steps, rope, visited):
+    head = rope[0]
+
+    for _ in range(steps):
+        point, step = UNIT_VECTORS[direction]
+        head[point] += step
+
+        for i in range(1, len(rope)):
+            pred = rope[i - 1]
+            succ = rope[i]
+
+            dx = pred[0] - succ[0]
+            dy = pred[1] - succ[1]
+
+            if (abs(dx) > abs(dy)):
+                succ[0] += dx - (dx // abs(dx))
+                succ[1] = pred[1]
+
+            elif (abs(dx) < abs(dy)):
+                succ[1] += dy - (dy // abs(dy))
+                succ[0] = pred[0]
+
+            else:
+                if (dx): succ[0] += dx - (dx // abs(dx))
+                if (dy): succ[1] += dy - (dy // abs(dy))
+
+        visited.add(tuple(rope[-1]))
+
+
+for move in puzzle.input_data.splitlines():
+    direction, steps = move.split()
+    make_move(direction, int(steps), rope, visited)
+
+
+puzzle.answer_a = len(visited)