把字符串转换成整数

 

 

 

 

 

class Solution:
    def strToInt(self, str: str) -> int:
        # 去除首尾空格
        str = str.strip()
        # 空字符串直接返回0
        if not str: return 0
        res, i, sign = 0, 1, 1
        int_max, int_min, boundry = 2**31-1, -2**32-1, 2**32//10
        if str[0] == '-': sign = -1  # 保存负号
        elif str[0] != '+': i = 0    # 若无符号位，则需从i=0开始数字拼接
        for c in str[i:]:
            if not '0' <= c <= '9': break   # 遇到非数字的字符就跳出
            # 数字越界处理
            if res > boundry or res == boundry and c>'7': return int_max if sign==1 else int_min
            # 数字拼接
            res = 10 * res + ord(c) - ord('0')
        return sign * res

　　https://leetcode-cn.com/leetbook/read/illustration-of-algorithm/58mttv/