Implement 2019 day 2

Start of the intcode madness

2019/aoc2019/intcode.py

@@ -0,0 +1,59 @@
+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
+