WA: Product

和前面的高精度加法一样，实在找不到原因，之前的大数从来没这样的。。

/* UVa 10106 - Product */
# include <stdio.h>
# include <string.h>

# define MAXN 252

char a[MAXN], b[MAXN];
char ss[2 * MAXN];

void pro(char *s);

int main()
{
     int lena, lenb, i, j, tmp;
     
     while (~scanf("%s", a))
     {
           scanf("%s", b);
           lena = strlen(a);
           lenb = strlen(b);
           pro(a);
           pro(b);
           memset(ss, 0, sizeof(ss));
            for (i = 0; i < lena; ++i)
           for (j = 0; j < lenb; ++j)
           {
                 tmp = a[i]*b[j] + ss[i+j];
                 ss[i+j] = tmp % 10;
                 ss[i+j+1] += tmp / 10;
            }
            for (i = MAXN-1; i >= 0; --i)
                  if (ss[i] != 0) break;
            if (i < 0) printf("%d", ss[0]);
            else while (i >= 0) printf("%d",ss[i--]);
           printf("\n");
      }
      
     return 0;
}

void pro(char *s)
{
      int len, i, c, tmp;
      len = strlen(s);
      tmp = len / 2;
      for (i = 0; i < tmp; ++i)
      {
           c = s[i] - '0';
           s[i] = s[len-1-i] - '0';
           s[len-1-i] = c;
     }
     if (len % 2) s[tmp] -= '0';
}