题解 | #把字符串转换成整数(atoi)#
把字符串转换成整数(atoi)
https://www.nowcoder.com/practice/d11471c3bf2d40f38b66bb12785df47f
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
#
# @param s string字符串
# @return int整型
#
INT_MAX = 2 ** 31 - 1
INT_MIN = -2 ** 31
class Automaton:
def __init__(self):
self.state = 'start'
self.sign = 1
self.ans = 0
# 状态转移
self.table = {
'start': ['start', 'signed', 'in_number', 'end'],
'signed': ['end', 'end', 'in_number', 'end'],
'in_number': ['end', 'end', 'in_number', 'end'],
'end': ['end', 'end', 'end', 'end'],
}
# 返回输入c之后的状态
def get_col(self, c):
if c.isspace():
return 0
if c == '+' or c == '-':
return 1
if c.isdigit():
return 2
return 3
# 迭代转换每个字符为数字self.ans，记录符号位self.sign
def get(self, c):
self.state = self.table[self.state][self.get_col(c)]
if self.state == 'in_number':
self.ans = self.ans * 10 + int(c)
self.ans = min(self.ans, INT_MAX) if self.sign == 1 else min(self.ans, -INT_MIN)
elif self.state == 'signed':
self.sign = 1 if c == '+' else -1
class Solution:
def StrToInt(self, s: str) -> int:
automaton = Automaton()
for c in s:
if automaton.state == 'end': break
automaton.get(c)
return automaton.sign * automaton.ans
