Package g1001_1100.s1041_robot_bounded_in_circle

Class Solution

  • public class Solution
extends Object
    1041 - Robot Bounded In Circle.

    Medium

    On an infinite plane, a robot initially stands at (0, 0) and faces north. Note that:

    • The north direction is the positive direction of the y-axis.
    • The south direction is the negative direction of the y-axis.
    • The east direction is the positive direction of the x-axis.
    • The west direction is the negative direction of the x-axis.

    The robot can receive one of three instructions:

    • "G": go straight 1 unit.
    • "L": turn 90 degrees to the left (i.e., anti-clockwise direction).
    • "R": turn 90 degrees to the right (i.e., clockwise direction).

    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 is initially at (0, 0) facing the north direction.

    “G”: move one step. Position: (0, 1). Direction: North.

    “G”: move one step. Position: (0, 2). Direction: North.

    “L”: turn 90 degrees anti-clockwise. Position: (0, 2). Direction: West.

    “L”: turn 90 degrees anti-clockwise. Position: (0, 2). Direction: South.

    “G”: move one step. Position: (0, 1). Direction: South.

    “G”: move one step. Position: (0, 0). Direction: South.

    Repeating the instructions, the robot goes into the cycle: (0, 0) –> (0, 1) –> (0, 2) –> (0, 1) –> (0, 0).

    Based on that, we return true.

    Example 2:

    Input: instructions = “GG”

    Output: false

    Explanation: The robot is initially at (0, 0) facing the north direction.

    “G”: move one step. Position: (0, 1). Direction: North.

    “G”: move one step. Position: (0, 2). Direction: North.

    Repeating the instructions, keeps advancing in the north direction and does not go into cycles.

    Based on that, we return false.

    Example 3:

    Input: instructions = “GL”

    Output: true

    Explanation: The robot is initially at (0, 0) facing the north direction.

    “G”: move one step. Position: (0, 1). Direction: North.

    “L”: turn 90 degrees anti-clockwise. Position: (0, 1). Direction: West.

    “G”: move one step. Position: (-1, 1). Direction: West.

    “L”: turn 90 degrees anti-clockwise. Position: (-1, 1). Direction: South.

    “G”: move one step. Position: (-1, 0). Direction: South.

    “L”: turn 90 degrees anti-clockwise. Position: (-1, 0). Direction: East.

    “G”: move one step. Position: (0, 0). Direction: East.

    “L”: turn 90 degrees anti-clockwise. Position: (0, 0). Direction: North.

    Repeating the instructions, the robot goes into the cycle: (0, 0) –> (0, 1) –> (-1, 1) –> (-1, 0) –> (0, 0).

    Based on that, we return true.

    Constraints:

    • 1 <= instructions.length <= 100
    • instructions[i] is 'G', 'L' or, 'R'.

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • isRobotBounded

        public boolean isRobotBounded​(String instructions)