题目：Implement atoi to convert a string to an integer.

思路：一路走下去

注意最大值最小值

代码：

class Solution {public://https://leetcode.com/problems/string-to-integer-atoi/    int myAtoi(string str) {        int result=0;                int i=0,sign=1;        int length=str.length();                while(str[i]==' '){            i++;        }//找到非空值                if(str[i]=='+'){            sign=1;            i++;        }else if(str[i]=='-'){//完美解决没有符号问题            sign=-1;            i++;        }                while(   '0'<=str[i]&&str[i]<='9'   ){            if(result>INT_MAX/10){                return sign==1?INT_MAX:INT_MIN;            }            if(result==INT_MAX/10){                if(sign==1){                    return str[i]>'7'?(INT_MAX):(result*10+(str[i]-'0'));                }                if(sign==-1){                    return str[i]>='8'?(INT_MIN):-(result*10+(str[i]-'0'));                }            }            result=result*10+(str[i]-'0');            i++;        }                return result*sign;    }};