leetcode[8] 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.

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.

class Solution {public:int myAtoi(string str) {int a = 0, b = 0;int i = 0;int t = 0;while (str[t] == ' ') t++;i = t;if (str[t] == '-'|| str[t] == '+') i++;//while (str[i] == ' ') i++;if (str[t] == '-')for (; i < str.length(); i++) {b = a;if (str[i] - '0' < 0 || str[i] - '0'>9) break;a = a * 10 - str[i] + '0';if (a / 10 != b) return INT_MIN;}else for (; i < str.length(); i++) {b = a;if (str[i] - '0' < 0 || str[i] - '0'>9) break;a = a * 10 + str[i] - '0';if (a / 10 != b) return INT_MAX;}return a;}};