【LeetCode 65】Valid Number （Python）_python leetcode 65

有限状态机：https://blog.csdn.net/suwei19870312/article/details/12094233

class Solution(object):
    def isNumber(self, s):
        """
        :type s: str
        :rtype: bool
        """
        if not s:
            return False
        INVALID = 0
        SPACE = 1
        SIGN = 2
        DIGIT = 3
        DOT = 4
        E = 5
 
        transition = [
            [-1,0,3,1,2,-1],
            [-1,8,-1,1,4,5],
            [-1,-1,-1,4,-1,-1],
            [-1,-1,-1,1,2,-1],
            [-1,8,-1,4,-1,5],
            [-1,-1,6,7,-1,-1],
            [-1,-1,-1,7,-1,-1],
            [-1,8,-1,7,-1,-1],
            [-1,8,-1,-1,-1,-1]
        ]
 
        state = 0
        for i in s:
            if i == ' ':
                idx = SPACE
            elif i == '-' or i == '+':
                idx = SIGN
            elif i >= '0' and i <= '9':
                idx = DIGIT
            elif i == '.':
                idx = DOT
            elif i == 'E' or i == 'e':
                idx = E
            else:
                idx = INVALID
            state = transition[state][idx]
            if state == -1:
                return False
        return state == 1 or state == 4 or state == 7 or state == 8