2017: d08: ex2: add solution

2017/d08/ex2/ex2.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python
+
+import enum
+import itertools
+import operator
+import sys
+from collections import defaultdict
+from typing import NamedTuple
+
+
+class Operation(enum.StrEnum):
+    INC = "inc"
+    DEC = "dec"
+
+
+class Comparator(enum.StrEnum):
+    GT = ">"
+    GE = ">="
+    LT = "<"
+    LE = "<="
+    EQ = "=="
+    NE = "!="
+
+    def __call__(self, lhs: int, rhs: int) -> bool:
+        return getattr(operator, self.name.lower())(lhs, rhs)
+
+
+class Condition(NamedTuple):
+    target: str
+    comp: Comparator
+    value: int
+
+    def eval(self, registers: dict[str, int]) -> bool:
+        return self.comp(registers[self.target], self.value)
+
+
+class Instruction(NamedTuple):
+    target: str
+    op: Operation
+    amount: int
+    condition: Condition
+
+
+def solve(input: str) -> int:
+    def parse_line(line: str) -> Instruction:
+        target, op, amount, _, comp_target, comp_op, comp_value = line.split()
+        return Instruction(
+            target,
+            Operation(op),
+            int(amount),
+            Condition(comp_target, Comparator(comp_op), int(comp_value)),
+        )
+
+    def parse(input: str) -> list[Instruction]:
+        return [parse_line(line) for line in input.splitlines()]
+
+    program = parse(input)
+    regs: dict[str, int] = defaultdict(int)
+    max_reg = 0
+    for instr in program:
+        if not instr.condition.eval(regs):
+            continue
+        regs[instr.target] += instr.amount * (1 if instr.op == Operation.INC else -1)
+        max_reg = max(itertools.chain(regs.values(), [max_reg]))
+    return max_reg
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()