065--Valid Number.md

Validate if a given string can be interpreted as a decimal number.

Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true
" -90e3   " => true
" 1e" => false
"e3" => false
" 6e-1" => true
" 99e2.5 " => false
"53.5e93" => true
" --6 " => false
"-+3" => false
"95a54e53" => false

Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one. However, here is a list of characters that can be in a valid decimal number:

Numbers 0-9
Exponent - "e"
Positive/negative sign - "+"/"-"
Decimal point - "."
Of course, the context of these characters also matters in the input.

Update (2015-02-10):
The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.

class Solution(object):
    def isNumber(self, s):
        """
        :type s: str
        :rtype: bool
        """
        #define a DFA
        # https://leetcode.com/problems/valid-number/discuss/23728/A-simple-solution-in-Python-based-on-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