2017/25

Author: balrok

2017/25/input.txt

@@ -0,0 +1,63 @@
+Begin in state A.
+Perform a diagnostic checksum after 12173597 steps.
+
+In state A:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state B.
+  If the current value is 1:
+    - Write the value 0.
+    - Move one slot to the left.
+    - Continue with state C.
+
+In state B:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state A.
+  If the current value is 1:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state D.
+
+In state C:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state A.
+  If the current value is 1:
+    - Write the value 0.
+    - Move one slot to the left.
+    - Continue with state E.
+
+In state D:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state A.
+  If the current value is 1:
+    - Write the value 0.
+    - Move one slot to the right.
+    - Continue with state B.
+
+In state E:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state F.
+  If the current value is 1:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state C.
+
+In state F:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state D.
+  If the current value is 1:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state A.
+

2017/25/run.py

@@ -0,0 +1,45 @@
+class State:
+    def __init__(self):
+        self.writ = [0,0]
+        self.move = [0,0]
+        self.cont = [0,0]
+    def run(self, tape, cursor):
+        val = tape.get(cursor, 0)
+        tape[cursor] = self.writ[val]
+        cursor += self.move[val]
+        return cursor, self.cont[val]
+
+def parse():
+    states = []
+    start = 0
+    diag = 0
+    state = None
+    condition = 0
+    for l in open("input.txt").read().split("\n"):
+        if not l:
+            continue
+        l=l[:-1]
+        s = l.split(" ")
+        if l[0] == "B":
+            start = ord(l[-1]) - 65
+        elif l[0] == "P":
+            diag = int(s[-2])
+        elif l[0] == "I":
+            state = State()
+            states.append(state)
+            condition = 0
+        elif l[6] == "W":
+            state.writ[condition] = int(l[-1])
+        elif l[6] == "M":
+            state.move[condition] = (-1,1)[l[-2]=="h"]
+        elif l[6] == "C":
+            state.cont[condition] = ord(l[-1]) - 65
+            condition = 1
+    return states, start, diag
+
+tape = {}
+cursor = 2
+states, current, diag = parse()
+for _ in range(diag):
+    cursor, current = states[current].run(tape, cursor)
+print(sum(tape.values()))