萌新刷题（十一）有效数字

"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true

class Solution(object):
  def isNumber(self, s):
      """
      :type s: str
      :rtype: bool
      """
      #define a DFA
      state = [{}, 
              {'blank': 1, 'sign': 2, 'digit':3, '.':4}, 
              {'digit':3, '.':4},
              {'digit':3, '.':5, 'e':6, 'blank':9},
              {'digit':5},
              {'digit':5, 'e':6, 'blank':9},
              {'sign':7, 'digit':8},
              {'digit':8},
              {'digit':8, 'blank':9},
              {'blank':9}]
      currentState = 1
      for c in s:
          if c >= '0' and c <= '9':
              c = 'digit'
          if c == ' ':
              c = 'blank'
          if c in ['+', '-']:
              c = 'sign'
          if c not in state[currentState].keys():         
              return False
          currentState = state[currentState][c]      
          if currentState not in [3,5,8,9]:  
              return False
      return True

class Solution(object):
    def isNumber(self, s):
        """
        :type s: str
        :rtype: bool
        """

        try:
            float(s)
        except ValueError:
            return False

        return True

class Solution(object):
    def isNumber(self, s):
        """
        :type s: str
        :rtype: bool
        """
        try:
            float(s)
            return True
        except:   
            return False