c - 我应该如何用指针算术来解决这个密码？

Question

问题如下:

Solve the following cipher using Pointer Arithmetic. The given string is GKQTEHIN. Define a pointer and set it to the letter ‘T’ in this string. Traverse the string forward and backward. Add/subtract a single value (key) between 1 and 5 to each letter to solve this cipher and form a meaningful word. Hint: You will be using this as you solve it.

希望这已经正确完成......

char given[]="GKQTEHIN";
char *pointer; 
pointer=&given[3];

pointer-=3;
printf("%c", *pointer-4);

pointer+=1;
printf("%c", *pointer+4);

pointer+=1;
printf("%c", *pointer-4);

pointer+=1;
printf("%c", *pointer-4);

pointer+=1;
printf("%c", *pointer+4);

pointer+=1;
printf("%c", *pointer+4);

pointer+=1;
printf("%c", *pointer-4);

pointer+=1;
printf("%c\n\n", *pointer+4);

打印出“COMPILER”一词。

Answer 1

How do I "add/subtract a single value...to each alphabet"?

计算机只能理解和处理数字，因为计算机中的一切都是数字(或可以被视为数字)。这意味着字母内部实际上是数字。 C 中的 char 使用 ASCII encoding ，这使得每个字母对应一个数字。因此，您只需将 key 添加到表示该 char 的代码中即可。您可以毫无问题地使用 char 作为数字。

char a = 'a';
a++;
printf("%c\n", a); // prints 'b'