image.png
image.png
image.png
根据状态图进行下面的状态的定义
image.png
class Solution:
def isNumber(self, s: str) -> bool:
states = [
#每一行代表图上面的一个点
{ ' ': 0, 's': 1, 'd': 2, '.': 4 }, # 0. start with 'blank'
{ 'd': 2, '.': 4 } , # 1. 'sign' before 'e'
{ 'd': 2, '.': 3, 'e': 5, ' ': 8 }, # 2. 'digit' before 'dot'
{ 'd': 3, 'e': 5, ' ': 8 }, # 3. 'digit' after 'dot'
{ 'd': 3 }, # 4. 'digit' after 'dot' (‘blank’ before 'dot')
{ 's': 6, 'd': 7 }, # 5. 'e'
{ 'd': 7 }, # 6. 'sign' after 'e'
{ 'd': 7, ' ': 8 }, # 7. 'digit' after 'e'
{ ' ': 8 } # 8. end with 'blank'
]
p = 0 # start with state 0
for c in s:
if '0' <= c <= '9': t = 'd' # digit
elif c in "+-": t = 's' # sign
elif c in "eE": t = 'e' # e or E
elif c in ". ": t = c # dot, blank
else: t = '?' # unknown
if t not in states[p]: return False
p = states[p][t]
return p in (2, 3, 7, 8)
