Robot Bounded In Circle

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 degress 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: "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: "GG" Output: false Explanation: The robot moves north indefinitely.

Example 3:

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

Note:

  1. 1 <= instructions.length <= 100

  2. instructions[i] is in {'G', 'L', 'R'}

 class Solution {

       public boolean isRobotBounded(String ins) {
        int x = 0, y = 0, length = ins.length(), i = 0, dir[][] = {{0, 1}, {1, 0}, {0, -1}, { -1, 0}};
        for (int j = 0; j < length; ++j)
            if (ins.charAt(j) == 'R')
                i = (i + 1) % 4;
            else if (ins.charAt(j) == 'L')
                i = (i + 3) % 4;
            else {
                x += dir[i][0]; y += dir[i][1];
            }
        return x == 0 && y == 0 || i > 0;
    }
}

Here let's take following assumptions,

A robot is starting at (0,0) and faces north (i.e.,) (0,1) and after one sequence of instructions,

1) If a robot returns to (0,0), then it forms a circle.

2) If robot finishes with face not towards north, it will get back to the initial status in another one or three sequences.

(x,y) is a location of robot

dir[][] - direction a robot is facing

i = (i+1)%4 -> robot turns right

i = (i+3)%4 -> robot turns left

3) Check final status after all instructions.

 

 

The intention behind this blog is to help all my fellow programmers. Also to provide solutions for various coding platform problems with solution and explanation. I will add many tutorials in future. I am not a professional blogger but whenever time permits I will post. I hope you’ll enjoy the content and find it useful! Check out my Writer blog for a more valuable quotes. For any queries or suggestions, please feel free to reach out to me. Happy coding!

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