1041. Robot Bounded In Circle

Medium

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On an infinite plane, a robot initially stands at (0, 0) and faces north. The robot can receive one of three instructions:

• "G": go straight 1 unit;

• "L": turn 90 degrees to the left;

• "R": turn 90 degrees to the right.

The robot performs the instructions given in order, and repeats them forever.

Return true if and only if there exists a circle in the plane such that the robot never leaves the circle.

Example 1:

Input: instructions = "GGLLGG"
Output: true
Explanation: The robot moves from (0,0) to (0,2), turns 180 degrees, and then returns to (0,0).
When repeating these instructions, the robot remains in the circle of radius 2 centered at the origin.

Example 2:

Input: instructions = "GG"
Output: false
Explanation: The robot moves north indefinitely.

Example 3:

Input: instructions = "GL"
Output: true
Explanation: The robot moves from (0, 0) -> (0, 1) -> (-1, 1) -> (-1, 0) -> (0, 0) -> ...

Constraints:

• 1 <= instructions.length <= 100

• instructions[i] is 'G', 'L' or, 'R'.

class Solution:
    def isRobotBounded(self, instructions: str) -> bool:
        point = 'N'
        x ,y = 0,0
        for char in instructions:
            if char == 'G':
                x,y = self.move(point, [x,y])
                # print(point, x, y)
            elif char == 'L':
                if point == 'N':
                    point = 'W'
                elif point == 'W':
                    point = 'S'
                elif point == 'S':
                    point = 'E'
                else:
                    point = 'N'
            elif char == 'R':
                if point == 'N':
                    point = 'E'
                elif point == 'E':
                    point = 'S'
                elif point == 'S':
                    point = 'W'
                else:
                    point = 'N'
        # print('Final',point, x, y)
        return True if point != 'N' or (x == 0 and y == 0) else False
                
    def move(self, point, coordinates):
        x,y = coordinates[0], coordinates[1]
        if point == 'N':
            y += 1
        elif point == 'E':
            x += 1
        elif point == 'W':
            x -= 1
        else:
            y -= 1
        return [x,y]py