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.

public class Solution {
public int MyAtoi(string str) {
int i = 0;
while (i < str.Length && str[i] == ' ')
++i;
if (i == str.Length)
return 0;
int sign = 1;
if (str[i] == '+')
++i;
else if (str[i] == '-')
{
++i;
sign = -1;
}
if (i == str.Length)
return 0;

long ret = 0;
while (i < str.Length && char.IsDigit(str[i]))
{
ret = ret * 10 + (str[i] - '0');
if (sign > 0 && ret >= int.MaxValue)
return int.MaxValue;
if (sign < 0 && ret > int.MaxValue)
return int.MinValue;
++i;
}
return (int)(sign * ret);
}
}