eetcode 之String to Integer (atoi)（28）

int atoi(char *str)
{
int len = strlen(str);
int sign = 1;
int num = 0;

int i = 0;
while (str[i] == ' '&& i < len)i++;

if (str[i] == '+')i++;
else if (str[i] == '-')
{
sign = -1;
i++;
}

for (; i < len; i++)
{
if (str[i]<'0'&&str[i]>'9')break;
if (num>INT_MAX / 10 || (num==INT_MAX / 10 && (str[i] - '0')>INT_MAX % 10))
{
return sign == -1 ? INT_MIN : INT_MAX;
}
num = num * 10 + str[i] - '0';
}

return num*sign;
}