Leetcode: String to Integer (atoi)

题目：

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.

参考代码：

#define INT_MAX 2147483647#define INT_MIN (-INT_MAX-1)class Solution {public:    int atoi(const char *str)    {    if (str == nullptr)    {    return 0;    }    int position = 0;    while (str[position] == ' ')    {    position++;    }    if (str[position] == '\0')    {    return 0;    }        int signal = 1;    if (str[position] == '+' || str[position] == '-')    {    if (str[position] == '-')    {    signal = -1;    }    position++;    }        long long result = 0;// 注意这里是long long    while (str[position] >= '0' && str[position] <= '9')    {    result = result * 10 + str[position] - '0';    if (result * signal > INT_MAX)    {    return INT_MAX;    }    if (result * signal < INT_MIN)    {    return INT_MIN;    }        position++;    }    return result * signal;    }};