LeetCode-String to Integer (atoi) -解题报告

原题链接 https://leetcode.com/problems/string-to-integer-atoi/

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. 

实现atoi的功能。

我就说一下有一些注意的地方。

1. 字符串开始可能有空白符需要跳过。
2. 正负数的情况。
3. 数值超过了int的表示范围

class Solution {public:    int myAtoi(string str) {int pos = 0;long long ans = 0;bool sign = true;while (str[pos] == ' ')pos++;if (str[pos] == '-')sign = false, pos++;else if(str[pos] == '+')pos++;while (pos < str.length()){int tmp = str[pos] - '0';if(tmp >= 0 && tmp <= 9)ans = ans * 10 + tmp;else break;if (ans > INT_MAX || ans < INT_MIN)return sign ? INT_MAX : INT_MIN;pos++;}return sign ? ans : -ans;}};