题解 | #把字符串转换成整数(atoi)#

#
# 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
#
class Solution:
    def StrToInt(self , s: str) -> int:
        # write code here
        s = s.strip()
        flag = 1
        sta = False
        res = 0
        for i in range(len(s)):
            c = s[i]
            if not c.isdigit():
                if sta==False:
                    if c !='+' and c !='-':
                        return 0
                    elif c == '-':
                        flag = -1
                        sta = True
                    elif c =='+':
                        flag = 1
                        sta = True
                else:
                    break
                    
            else:
                sta = True
                res = res * 10 +  flag*(ord(c)-ord('0'))
        
        if res>2**31 -1:
            res = 2**31 -1
        elif res<-2**31:
            res = -2**31
        return res