8

solutions/8/README.md

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+# 8
+
+Keep getting better! Today we write a little state machine, love it.
+
+So firstly we remember what `oc` (Operation Counter) we have already visited and if so we simply stop and return the accumulator.
+
+For I basically run the code many times, inverting `nop` to `jmp` and vice versa until i found a working instruction set.
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>1087</li>
+    <li>780</li>
+  </ol>
+</details>

solutions/8/python/main.py

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+from os.path import join, dirname
+from typing import List, Optional, Set, Tuple
+
+Instructions = List[Tuple[str, int]]
+
+
+class VM:
+    def __init__(self, code: str) -> None:
+        instructionsRaw = code.strip().split('\n')
+        self.acc = 0
+        self.oc = 0
+        self.invert: Optional[int] = None
+        self.instructions: Instructions = []
+        for instruction in instructionsRaw:
+            op, value = instruction.split(' ')
+            self.instructions.append((op, int(value)))
+
+    def reset(self):
+        self.acc = 0
+        self.oc = 0
+
+    def exec(self):
+        op, value = self.instructions[self.oc]
+        if self.oc == self.invert:
+            op = 'jmp' if op == 'nop' else 'nop'
+        if op == 'nop':
+            self.oc += 1
+        elif op == 'acc':
+            self.acc += value
+            self.oc += 1
+        elif op == 'jmp':
+            self.oc += value
+
+    def run(self) -> Tuple[int, bool]:
+        self.reset()
+        already_visited: Set[int] = set()
+        m = len(self.instructions)
+        while True:
+            if self.oc in already_visited:
+                return (self.acc, True)
+            if not self.oc < m:
+                return (self.acc, False)
+            already_visited.add(self.oc)
+            self.exec()
+
+    def fix(self):
+        for i, instruction in enumerate(self.instructions):
+            op, _ = instruction
+            if op == 'nop' or op == 'jmp':
+                self.invert = i
+                acc, error = self.run()
+                if not error:
+                    return acc
+
+
+data = join(dirname(__file__), '../data.txt')
+with open(data) as f:
+    vm = VM(f.read())
+
+    acc, err = vm.run()
+    print(acc)
+
+    print(vm.fix())