Implement 2019 day 2

Start of the intcode madness

2019/aoc2019/day02.py

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+from typing import TextIO
+
+from aoc2019.intcode import read_program, Computer
+
+
+def part1(data: TextIO) -> int:
+    program = read_program(data)
+
+    program[1] = 12
+    program[2] = 2
+
+    computer = Computer(program)
+    computer.run()
+
+    return computer[0]
+
+
+def part2(data: TextIO) -> int:
+    program = read_program(data)
+
+    for verb in range(100):
+        for noun in range(100):
+            computer = Computer(program.copy())
+
+            computer[1] = noun
+            computer[2] = verb
+
+            computer.run()
+
+            if computer[0] == 19690720:
+                return 100 * noun + verb
+
+    raise ValueError('Did not find valid combination')

2019/aoc2019/intcode.py

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+from typing import List, TextIO
+
+
+def read_program(data: TextIO) -> List[int]:
+    line = next(data)
+
+    return [int(i) for i in line.split(',')]
+
+
+class Computer:
+    program: List[int]
+    pointer: int
+
+    def __init__(self, program: List[int], pointer: int = 0) -> None:
+        self.program = program
+        self.pointer = pointer
+
+    def __getitem__(self, item: int) -> int:
+        self._ensure_length(item + 1)
+        return self.program[item]
+
+    def __setitem__(self, key: int, value: int) -> None:
+        self._ensure_length(key + 1)
+        self.program[key] = value
+
+    def _ensure_length(self, length: int) -> None:
+        if len(self.program) < length:
+            # Double current program size with 0s
+            self.program.extend(0 for _ in range(len(self.program)))
+
+    def run(self) -> None:
+        """ Run until failure"""
+        while self._execute_current():
+            pass
+
+    def _execute_current(self) -> bool:
+        """
+        Execute a single instruction
+        :return: True if the program should continue
+        """
+        pointer = self.pointer
+        opcode = self[pointer]
+
+        if opcode == 1:
+            # Add
+            self[self[pointer + 3]] = self[self[pointer + 1]] + self[self[pointer + 2]]
+            self.pointer += 4
+        elif opcode == 2:
+            # Multiply
+            self[self[pointer + 3]] = self[self[pointer + 1]] * self[self[pointer + 2]]
+            self.pointer += 4
+        elif opcode == 99:
+            # Halt
+            return False
+        else:
+            raise ValueError(f'Unknown opcode {opcode} at {pointer}')
+
+        return True
+

2019/tests/test_intcode.py

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+from typing import List
+
+import pytest
+
+from aoc2019.intcode import Computer
+
+
+@pytest.mark.parametrize('program,expected', [
+    ([1, 9, 10, 3, 2, 3, 11, 0, 99, 30, 40, 50], [3500, 9, 10, 70, 2, 3, 11, 0, 99, 30, 40, 50]),
+    ([1, 0, 0, 0, 99], [2, 0, 0, 0, 99]),
+    ([2, 3, 0, 3, 99], [2, 3, 0, 6, 99]),
+    ([2, 4, 4, 5, 99, 0], [2, 4, 4, 5, 99, 9801]),
+    ([1, 1, 1, 4, 99, 5, 6, 0, 99], [30, 1, 1, 4, 2, 5, 6, 0, 99])
+])
+def test_instructions_day2(program: List[int], expected: List[int]) -> None:
+    computer = Computer(program)
+
+    computer.run()
+
+    assert computer.program == expected