个人记录-LeetCode 8.String to Integer (atoi)

问题
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.

思路极其简单，但没有约定何为真正有效的输入，实际上只能试错然后修改。
在现在这个时间点，服务器认为一个有效的字符串在前面可以出现空格；从非空格开始，可以用”+”、“-”后必须立即连接实际的数字。

代码示例：

public class Solution {    public int myAtoi(String str) {        if (str == null) {            return 0;        }        char[] sChar = str.toCharArray();        int len  = sChar.length;        if (len <= 0) {            return 0;        }        int beginIndex = 0;        //跳过空格        for (int i = 0; i < len; ++i) {            if (sChar[i] == ' ') {                ++beginIndex;            } else {                break;            }        }        boolean negative = false;        //判断是否以+、-号开头        if (sChar[beginIndex] == '-') {            negative = true;            ++beginIndex;        } else if (sChar[beginIndex] == '+') {            ++beginIndex;        }        long result = 0;        for (int i = beginIndex; i < len; ++i) {            int temp = sChar[i] - '0';            //判断是否为数字，不是的话则结束解析            if (temp >=0 && temp <=9) {                result = result * 10 + temp;                if (result > Integer.MAX_VALUE) {                    if (negative) {                        return Integer.MIN_VALUE;                    } else {                        return Integer.MAX_VALUE;                    }                }            } else {                break;            }        }        if (negative) {            result *= -1;        }        return (int)result;    }}