c - 十六进制到十进制/十进制到十六进制程序。无法让程序为 char 数组打印字符串

Question

我正在编写一个将十六进制转换为十进制并将十进制转换为十六进制的程序。我写了两个函数:itox(hexstring, n) 和 int xtoi(hexstring)。这两个功能由驱动程序实现。当我使用 printf 返回 int 和 hexstring 时，hexstring 永远不会出现在输出中。此外，该程序似乎从未进入 xtoi() 函数内的 printf 语句。这是我得到的输出:

--------------:~/cs240/hw3$ gcc showxbits.c xbits.c -o showxbits
--------------:~/cs240/hw3$ ./showxbits
in itox, processing 47
                  47             0

我是 C 的新手。下面是我的代码。任何建议表示赞赏。

驱动代码为:

  1 /*
  2  *  stub driver for functions to study integer-hex conversions
  3  *
  4  */
  5
  6 #include <stdio.h>
  7 #include "xbits.h"
  8
  9 #define ENOUGH_SPACE 100 /* not really enough space */
 10
 11 int main() {
 12   char hexstring[ENOUGH_SPACE];
 13   int m = 0, n = 47;
 14   itox( hexstring, n);
 15   printf("%s", hexstring);
 16
 17   /* for stub testing: create a fake input string*/
 18
 19   m= xtoi(hexstring);
 20
 21   printf("\t%12d %s %12d\n", n, hexstring, m);
 22
 23   return 0;  /* everything is just fine */
 24 }
 25
 26

这两个函数的代码是:

  1 /*
  2  *  stubs for functions to study
  3  *  integer-hex conversions
  4  *
  5  */
  6
  7 #include <stdio.h>
  8 #include "xbits.h"
  9
 10 /* function represents the int n as a hexstring which it places in the
 11 hexstring array */
 12
 13 void itox( char hexstring[], int n) {
 14         char hexkey[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
 15         int rem;
 16         int res = n;
 17         int i;
 18         for(i = 0; res < 16; i++){
 19                 rem = res%16;
 20                 res = res/16;
 21                 hexstring[i] = hexkey[rem];
 22         }
 23         i++;
 24         hexstring[i] = hexkey[res];
 25         i++;
 26         hexstring[i] = '\0';
 27
 28    printf("in itox, processing %d\t%s\n", n, hexstring);
 29 }
 30
 31 /* function converts hexstring array to equivalent integer value  */
 32
 33 int xtoi( char hexstring[]) {
 34         int cursor;
 35         int count = 0;
 36         char current;
 37         int dec = 0;
 38         int pow = 1;
 39         int i;
 40         int j;
 41         char hexkey[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
 42
 43         for(cursor = (2*sizeof(char)); cursor >= 0; --cursor){
 44                 current = hexstring[cursor];
 45                 for(i = 0; i < 16; ++i){
 46                         if(current == hexkey[i]){
 47                                 if(count == 0){
 48                                         dec = dec + i;
 49                                 }
 50                                 else{
 51                                         for(j = 0; j < count; j++)
 52                                                 pow = pow * 16;
 53                                 dec = dec + pow*i;
 54                                 pow = 1;
 55                                 }
 56                         }
 57                 }
 58                 ++count;
 59         }
 60         return dec;
 61
 62   printf("in xtoi, processing %s\n", hexstring);
 63 }
 64

Answer 1

缺少单引号

char hexkey[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
                 ^ ^


 0=='\0' ==> Nul character used to terminate strings.

 0!='0'    

'0' ASCII value 48 

---

你错了

for(i = 0; res < 16; i++){     
               ^ 
                  rem = res%16;
                  res = res/16;
                 hexstring[i] = hexkey[rem];
         }

for 循环条件错误。

   n==47 ==> res==47 and res<16 ==> 47 < 16 failed.   

---

像这样修改

for(i = 0; res >0; i++)
         {
                  rem = res%16;
                  res = res/16;
                  hexstring[i] = hexkey[rem];
         }
                   hexstring[i] = '\0';

 printf("in itox, processing %d==%s\n", n, hexstring); // You need to reverse it.