题目
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.
解题思路
经过一系列的操作，主要回到原点，或者朝向与最开始不同，就可以形成一个圈
代码
class Solution:
def isRobotBounded(self, instructions: str) -> bool:
x = y = 0
d = (0, 1)
for c in instructions:
if c == 'G':
x, y = x + d[0], y + d[1]
elif c =='L':
d = (-d[1], d[0])
else:
d = (d[1], -d[0])
return (x == 0 and y == 0) or d != (0, 1)
