atoi:convert string to integer;2.0

#include <ctype.h>
/*atoi : convert s to integer; version 2 */
int atoi(char s[])
{
   int i, n, sign;

   for (i =0; isspace(s[i]);i++)  /*skip white space */
           ;
   sign = (s[i] == '-') ? -1 ; 1;
   if (s[i] == '+' || s[i] == '-')  /*skip sign */
         i++;
   for(n = 0;isdigit(s[i]); i++)
       n =10 * n + (s[i] - '0');
   return sign * n;
}