leetcode1041

class Solution:
    def isRobotBounded(self, instructions: str) -> bool:
        vec = [0,0,0]
        #0 up(north),1 left(west),2 down(south),3 right(east)
        for ins in instructions:
            if ins == 'G':
                if vec[2] == 0:
                    vec[1] += 1
                elif vec[2] == 1:
                    vec[0] -= 1
                elif vec[2] == 2:
                    vec[1] -= 1
                else:
                    vec[0] += 1
            elif ins =='L':
                vec[2] = (vec[2] + 1) % 4
            elif ins == 'R':
                vec[2] = (vec[2] +3) % 4
        #print(vec)
        if vec[0]==0 and vec[1]==0:
            return True
        elif vec[2] != 0:
            return True
        else :
            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。。。