2023 dec 8th

Python/2023/08/main.py

@@ -0,0 +1,57 @@
+import math
+
+input = open("input", 'r')
+
+instructions = input.readline().rstrip()
+data = {}
+all_nodes = []
+
+_ = input.readline()
+
+for line in input:
+    line = line.rstrip()
+    node, nexts = line.split(" = ")
+    left, right = nexts.split(", ")
+
+    all_nodes.append(node)
+
+    data[node] = {
+        "left": left[1:],
+        "right": right[:-1]
+    }
+
+
+current = "AAA"
+inst = 0
+
+steps = 0
+
+while current != "ZZZ":
+    go = instructions[inst]
+    steps += 1
+    inst = (inst + 1) % len(instructions)
+    if go == "L":
+        current = data[current]["left"]
+    else:
+        current = data[current]["right"]
+
+print(steps)
+
+def fromAToZ(start, ends):
+    current = start
+    inst = 0
+    steps = 0
+
+    while current not in ends:
+        go = instructions[inst]
+        steps += 1
+        inst = (inst + 1) % len(instructions)
+        direct = "left" if go == "L" else "right"
+        current = data[current][direct]
+
+    return steps
+
+starts = [node for node in all_nodes if node[-1] == "A"]
+ends = [node for node in all_nodes if node[-1] == "Z"]
+
+print(math.lcm(*[fromAToZ(start, ends) for start in starts]))