day07b.py

import itertools


def main():
    with open('day07_input.txt') as file:
        contents = file.read()

    program = contents.strip().split(',')

    phase_seq = itertools.permutations(range(5, 10))
    # phase_seq = [(9, 8, 7, 6, 5)]

    max_thruster = 0
    for seq in phase_seq:
        val = 0

        seq = list(seq)
        running_programs = [[program[:], 0] for _ in range(5)]
        inputs = [0]
        prog_indx = 0

        while True:
            if seq:
                inputs.insert(0, seq.pop(0))

            curr_program = running_programs[prog_indx]
            output, curr_program[1] = run_program(curr_program[0], curr_program[1], inputs)

            if output is None:
                if prog_indx == 0:
                    val = inputs[0]
                    break
            else:
                inputs.append(output)

            prog_indx = (prog_indx + 1) % 5

        max_thruster = max(max_thruster, val)

    print(f'the max is {max_thruster}')


def run_program(program, curr_indx, inputs):
    while True:
        # Read the instruction at the instruction pointer
        instr = program[curr_indx].zfill(5)

        # Extract the opcode and parameter modes
        opcode = int(instr[-2:])
        modes = [int(x) for x in list(instr[2::-1])]

        # convenience function for interpreting parameter modes
        def get_arg_value(arg, mode):
            return int(program[arg]) if mode == 0 else arg

        if opcode in [1, 2, 7, 8]:
            # All three parameter ops that write a result to a given location
            args = [int(program[curr_indx + i]) for i in range(1, 4)]

            p1 = get_arg_value(args[0], modes[0])
            p2 = get_arg_value(args[1], modes[1])

            if opcode == 1:
                result = p1 + p2
            elif opcode == 2:
                result = p1 * p2
            elif opcode == 7:
                result = 1 if p1 < p2 else 0
            else:
                result = 1 if p1 == p2 else 0

            program[args[2]] = str(result)

            curr_indx += 4
        elif opcode in [5, 6]:
            # Two parameter jump ops that update the instruction pointer
            args = [int(program[curr_indx + i]) for i in range(1, 3)]

            p1 = get_arg_value(args[0], modes[0])
            p2 = get_arg_value(args[1], modes[1])

            if opcode == 5 and p1 != 0:
                curr_indx = p2
            elif opcode == 6 and p1 == 0:
                curr_indx = p2
            else:
                curr_indx += 3
        elif opcode == 3:  # Input
            dest = int(program[curr_indx + 1])
            program[dest] = str(inputs.pop(0))
            curr_indx += 2
        elif opcode == 4:  # Output
            source = int(program[curr_indx + 1])
            output = int(program[source])
            curr_indx += 2

            return output, curr_indx
        elif opcode == 99:  # Exit
            return None, None


if __name__ == '__main__':
    main()