Leetcode 1041. 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 <= instructions.length <= 100
instructions is in {'G', 'L', 'R'}
class Solution:
def isRobotBounded(self, instructions: str) -> bool:
# N,W,S,E
directions = [,[-1, 0],,]
direction = 0
x, y = 0, 0
for instruction in instructions:
if instruction == 'G':
x = x + directions
y = y + directions
elif instruction == 'L':
direction = (direction + 1) % 4
else:
direction = (direction + 3) % 4
return (x == 0 and y == 0) | direction != 0
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