leetcode1041

 1 class Solution:
 2     def isRobotBounded(self, instructions: str) -> bool:
 3         vec = [0,0,0]
 4         #0 up(north),1 left(west),2 down(south),3 right(east)
 5         for ins in instructions:
 6             if ins == 'G':
 7                 if vec[2] == 0:
 8                     vec[1] += 1
 9                 elif vec[2] == 1:
10                     vec[0] -= 1
11                 elif vec[2] == 2:
12                     vec[1] -= 1
13                 else:
14                     vec[0] += 1
15             elif ins =='L':
16                 vec[2] = (vec[2] + 1) % 4
17             elif ins == 'R':
18                 vec[2] = (vec[2] +3) % 4
19         #print(vec)
20         if vec[0]==0 and vec[1]==0:
21             return True
22         elif vec[2] != 0:
23             return True
24         else :
25             return False

这是什么数学原理呢？想不出来。GG GL，这道题的灵感是从魔兽来的么。。。