Medium, Array/String

將一個(gè)字符轉(zhuǎn)換為數(shù)字，開(kāi)頭和結(jié)尾的空格忽略。開(kāi)頭的‘+’和‘-’需要考慮。

Solution

此題的關(guān)鍵是防止溢出，最大數(shù)為2^31-1，最小數(shù)為-2^31

class Solution(object):
    def myAtoi(self, str):
        """
        :type str: str
        :rtype: int
        """
        if len(str) == 0 : return 0
        ls = list(str.strip())
        
        sign = -1 if ls[0] == '-' else 1
        if ls[0] in ['-','+'] : del ls[0]
        ret, i = 0, 0
        while i < len(ls) and ls[i].isdigit() :
            ret = ret*10 + ord(ls[i]) - ord('0')
            i += 1
        return max(-2**31, min(sign * ret,2**31-1))