剑指 Offer 20. 表示数值的字符串

请实现一个函数用来判断字符串是否表示数值（包括整数和小数）。例如，字符串"+100"、"5e2"、"-123"、"3.1416"、"-1E-16"、"0123"都表示数值，但"12e"、"1a3.14"、"1.2.3"、"+-5"及"12e+5.4"都不是。

PYthon 解答：
1.自动机状态转移

class Solution:
    def isNumber(self, s: str) -> bool:
        states = [
            {' ':0, 's':1, 'd':2, '.':4},
            {'d':2, '.':4, },
            {'d':2, '.':3, 'e':5, ' ':8},
            {'d':3, 'e':5, ' ':8},
            {'d':3},
            {'s':6, 'd':7},
            {'d':7},
            {'d':7, ' ':8},
            {' ':8}
        ]
        state = 0
        t = None
        for c in s:
            if '0' <= c <= '9':
                t = 'd'
            elif c in '+-':
                t = 's'
            elif c in 'eE':
                t = 'e'
            elif c in '. ':
                t = c 
            else:
                t = c
            if t in states[state].keys():
                state = states[state][t]
            else: return False
        if state in [2, 3, 7, 8]:
            return True
        else: return False