Leetcode String to Integer (atoi)

最新推荐文章于 2022-06-10 00:24:13 发布

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本文详细解析了atoi函数的实现逻辑，包括如何处理输入字符串中的空格、符号和数字，以及如何进行整数边界检查。通过案例分析，帮助开发者理解atoi函数的核心原理并提升编程技巧。

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

Update (2015-02-10):

The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.

class Solution:
    def atoi(self, str):
        lens = len(str);
        
        if lens == 0:
            return 0;
        
        i = 0;
        cnt = 1;
        sum = 0;
        
        while i < lens:
            if str[i] == ' ':
                i += 1;
            else:
                break;
            
        if str[i] == '-':
            cnt = -1;
            i += 1;
        elif str[i] == '+':
            cnt = 1;
            i += 1;
        elif str[i] < '0' or str[i] > '9':
            return 0;
        
        while i < lens and str[i] >= '0' and str[i] <= '9':
            sum = sum * 10 + ord(str[i])-ord('0');
            i += 1;
        
        sum = sum*cnt;
        
        if sum > 0x7fffffff:
            sum = 0x7fffffff;
        if sum < -2 ** 31:
            sum = -2 ** 31;
        return sum;