LeetCode 08:string to int(atoi)(C++实现)

原题描述：

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.

spoilers alert… click to show requirements for atoi.

输入一个字符串将其转换为整形并输出。
部分测试用例包括：
输入“0100”输出“100”
输入“-10”输出“-10”
输入“+2”输出“+2”
输入“ 01010”输出“1010”
输入“ +-12a23”输出“0”
伪代码：

class Solution {public:    int myAtoi(string str) {        long long res=0;        int i=0,flag=1;        while(str[i]==' '){            if(str[i]==' '){                i++;            }        }        if(str[i]=='-'||str[i]=='+'){            flag=(str[i]=='-')?-1:1;            i++;        }        while(i<str.size()&&str[i]>='0'&&str[i]<='9'){                 res=(str[i]-'0')+res*10;                if(res > INT_MAX)                      return flag<0 ? INT_MIN : INT_MAX;            i++;        }        return (int)res*flag;    }};