#include <stdio.h>
   /* count digits, white space, others */
   main()
   {
       int c, i, nwhite, nother;
       int ndigit[10];
       nwhite = nother = 0;
       for (i = 0; i < 10; ++i)
           ndigit[i] = 0;
       while ((c = getchar()) != EOF)
           if (c >= '0' && c <= '9')
               ++ndigit[c-'0'];
           else if (c == ' ' || c == '\n' || c == '\t')
               ++nwhite;
           else
               ++nother;
       printf("digits =");
       for (i = 0; i < 10; ++i)
           printf(" %d", ndigit[i]);
       printf(", white space = %d, other = %d\n",
           nwhite, nother);
   }



这个代码中 ++ndigit[c-'0'];怎么理解？直接++ndigit[c]不行吗？c-'0'表示什么？

数组的下标是正整数不就行了吗？

懂了  谢谢