Robot movement

robot_circle.py

#!/usr/bin/env python


class Point(object):

    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __repr__(self):
        return '{}({}, {})'.format(self.__class__.__name__, self.x, self.y)

    def __eq__(self, other):
        return self.x == other.x and self.y == other.y

    def __ne__(self, other):
        return self.x != other.x or self.y != other.y


class Position(object):
    NORTH = 'n'
    EAST = 'e'
    SOUTH = 's'
    WEST = 'w'

    def __init__(self, location, orientation):
        self.location = location
        self.orientation = orientation


class Robot(object):

    def __init__(self):
        self.location = Point(0, 0)
        self.orientation = Position.NORTH

    def go(self):
        if self.orientation == Position.NORTH:
            self.location = Point(self.location.x, self.location.y - 1)
        elif self.orientation == Position.EAST:
            self.location = Point(self.location.x + 1, self.location.y)
        elif self.orientation == Position.SOUTH:
            self.location = Point(self.location.x, self.location.y + 1)
        elif self.orientation == Position.WEST:
            self.location = Point(self.location.x - 1, self.location.y)

    def turn_right(self):
        if self.orientation == Position.NORTH:
            self.orientation = Position.EAST
        elif self.orientation == Position.EAST:
            self.orientation = Position.SOUTH
        elif self.orientation == Position.SOUTH:
            self.orientation = Position.WEST
        elif self.orientation == Position.WEST:
            self.orientation = Position.NORTH

    def turn_left(self):
        if self.orientation == Position.NORTH:
            self.orientation = Position.WEST
        elif self.orientation == Position.EAST:
            self.orientation = Position.NORTH
        elif self.orientation == Position.SOUTH:
            self.orientation = Position.EAST
        elif self.orientation == Position.WEST:
            self.orientation = Position.SOUTH


def circle_does_exist(commands):
    robot = Robot()
    steps = [Position(robot.location, robot.orientation)]

    for c in commands:
        if c == 'G':
            robot.go()
            steps.append(Position(robot.location, robot.orientation))
        elif c == 'R':
            robot.turn_right()
        elif c == 'L':
            robot.turn_left()

    # If the starting position is the same as the ending position, we are in
    # a circle that the bot never leaves.
    #
    # NOTE: This isn't correct and doesn't find all the possible circular paths
    if steps[0].location == steps[-1].location:
        return 'YES'

    return 'NO'


print(circle_does_exist('GRGGRGGRGRGLG'))