g1001_1100.s1041_robot_bounded_in_circle

Class Solution

java.lang.Object

g1001_1100.s1041_robot_bounded_in_circle.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 Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
boolean	isRobotBounded(String instructions)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

isRobotBounded

public boolean isRobotBounded(String instructions)