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biao-shi-shu-zhi-de-zi-fu-chuan-lcof.py
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biao-shi-shu-zhi-de-zi-fu-chuan-lcof.py
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# @Title: 表示数值的字符串 (表示数值的字符串 LCOF)
# @Author: KivenC
# @Date: 2020-09-02 13:40:38
# @Runtime: 356 ms
# @Memory: 13.7 MB
class Solution:
def isNumber(self, s: str) -> bool:
# pattern = re.compile(r'^\s*[+-]?(?:\d+\.?|\d*\.\d+)(?:[eE][+-]?\d+)?\s*$')
# return re.match(pattern, s) is not None
# 有限状态自动机
from enum import Enum
State = Enum("State", [
"STATE_INITIAL",
"STATE_INT_SIGN",
"STATE_INTEGER",
"STATE_POINT",
"STATE_POINT_WITHOUT_INT",
"STATE_FRACTION",
"STATE_EXP",
"STATE_EXP_SIGN",
"STATE_EXP_NUMBER",
"STATE_END",
])
Chartype = Enum("Chartype", [
"CHAR_NUMBER",
"CHAR_EXP",
"CHAR_POINT",
"CHAR_SIGN",
"CHAR_SPACE",
"CHAR_ILLEGAL",
])
def toChartype(ch: str) -> Chartype:
if ch.isdigit():
return Chartype.CHAR_NUMBER
elif ch.lower() == "e":
return Chartype.CHAR_EXP
elif ch == ".":
return Chartype.CHAR_POINT
elif ch == "+" or ch == "-":
return Chartype.CHAR_SIGN
elif ch == " ":
return Chartype.CHAR_SPACE
else:
return Chartype.CHAR_ILLEGAL
transfer = {
State.STATE_INITIAL: {
Chartype.CHAR_SPACE: State.STATE_INITIAL,
Chartype.CHAR_NUMBER: State.STATE_INTEGER,
Chartype.CHAR_POINT: State.STATE_POINT_WITHOUT_INT,
Chartype.CHAR_SIGN: State.STATE_INT_SIGN,
},
State.STATE_INT_SIGN: {
Chartype.CHAR_NUMBER: State.STATE_INTEGER,
Chartype.CHAR_POINT: State.STATE_POINT_WITHOUT_INT,
},
State.STATE_INTEGER: {
Chartype.CHAR_NUMBER: State.STATE_INTEGER,
Chartype.CHAR_EXP: State.STATE_EXP,
Chartype.CHAR_POINT: State.STATE_POINT,
Chartype.CHAR_SPACE: State.STATE_END,
},
State.STATE_POINT: {
Chartype.CHAR_NUMBER: State.STATE_FRACTION,
Chartype.CHAR_EXP: State.STATE_EXP,
Chartype.CHAR_SPACE: State.STATE_END,
},
State.STATE_POINT_WITHOUT_INT: {
Chartype.CHAR_NUMBER: State.STATE_FRACTION,
},
State.STATE_FRACTION: {
Chartype.CHAR_NUMBER: State.STATE_FRACTION,
Chartype.CHAR_EXP: State.STATE_EXP,
Chartype.CHAR_SPACE: State.STATE_END,
},
State.STATE_EXP: {
Chartype.CHAR_NUMBER: State.STATE_EXP_NUMBER,
Chartype.CHAR_SIGN: State.STATE_EXP_SIGN,
},
State.STATE_EXP_SIGN: {
Chartype.CHAR_NUMBER: State.STATE_EXP_NUMBER,
},
State.STATE_EXP_NUMBER: {
Chartype.CHAR_NUMBER: State.STATE_EXP_NUMBER,
Chartype.CHAR_SPACE: State.STATE_END,
},
State.STATE_END: {
Chartype.CHAR_SPACE: State.STATE_END,
},
}
st = State.STATE_INITIAL
for ch in s:
typ = toChartype(ch)
if typ not in transfer[st]:
return False
st = transfer[st][typ]
return st in [State.STATE_INTEGER, State.STATE_POINT, State.STATE_FRACTION, State.STATE_EXP_NUMBER, State.STATE_END]