LeetCode in Kotlin
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 <= 100instructions[i]is'G','L'or,'R'.
Solution
class Solution {
fun isRobotBounded(instructions: String): Boolean {
val dir = arrayOf(intArrayOf(0, 1), intArrayOf(-1, 0), intArrayOf(0, -1), intArrayOf(1, 0))
var i = 0
var x = 0
var y = 0
for (s in instructions.indices) {
if (instructions[s] == 'L') {
i = (i + 1) % 4
} else if (instructions[s] == 'R') {
i = (i + 3) % 4
} else {
x += dir[i][0]
y += dir[i][1]
}
}
return x == 0 && y == 0 || i != 0
}
}