LeetCode-Solutions/Python/valid-number.py at master · pythonpeixun/LeetCode-Solutions · GitHub

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# Time: O(n)

# Space: O(1)

class InputType(object):

INVALID = 0

SPACE = 1

SIGN = 2

DIGIT = 3

DOT = 4

EXPONENT = 5

# regular expression: "^\s*[\+-]?((\d+(\.\d*)?)|\.\d+)([eE][\+-]?\d+)?\s*$"

# automata: http://images.cnitblog.com/i/627993/201405/012016243309923.png

class Solution(object):

def isNumber(self, s):

"""

:type s: str

:rtype: bool

"""

transition_table = [[-1, 0, 3, 1, 2, -1], # next states for state 0

[-1, 8, -1, 1, 4, 5], # next states for state 1

[-1, -1, -1, 4, -1, -1], # next states for state 2

[-1, -1, -1, 1, 2, -1], # next states for state 3

[-1, 8, -1, 4, -1, 5], # next states for state 4

[-1, -1, 6, 7, -1, -1], # next states for state 5

[-1, -1, -1, 7, -1, -1], # next states for state 6

[-1, 8, -1, 7, -1, -1], # next states for state 7

[-1, 8, -1, -1, -1, -1]] # next states for state 8

state = 0

for char in s:

inputType = InputType.INVALID

if char.isspace():

inputType = InputType.SPACE

elif char == '+' or char == '-':

inputType = InputType.SIGN

elif char.isdigit():

inputType = InputType.DIGIT

elif char == '.':

inputType = InputType.DOT

elif char == 'e' or char == 'E':

inputType = InputType.EXPONENT

state = transition_table[state][inputType]

if state == -1:

return False

return state == 1 or state == 4 or state == 7 or state == 8

class Solution2(object):

def isNumber(self, s):

"""

:type s: str

:rtype: bool

"""

import re

return bool(re.match("^\s*[\+-]?((\d+(\.\d*)?)|\.\d+)([eE][\+-]?\d+)?\s*$", s))

LeetCode-Solutions/Python/valid-number.py at master · pythonpeixun/LeetCode-Solutions · GitHub

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