谜语（C语言） [英] A riddle (in C)

问题描述

有一个朋友给了我一个谜语：

A friend gave me a riddle:

#include<stdio.h>

#define TOTAL_ELEMENTS ((sizeof(array) / sizeof(array[0])))
  int array[] = {23,34,12,17,204,99,16};

  int main()
  {
      int d;
      for(d=-1;d <= (TOTAL_ELEMENTS-2);d++)
          printf("%d\n",array[d+1]);
      getchar();
      return 0;
  }

以上code被认为能打印所有数组元素，什么是在code中的问题（输出什么）？我认为，循环不会遍历甚至一度？

The above code is supposed to print all the array elements, what is the problem in the code (the output is nothing)? I think the loop doesn't iterate even once?

我发现下面的code 确实工作

I found out that the following code does work:

#include<stdio.h>



#define TOTAL_ELEMENTS ((sizeof(array) / sizeof(array[0])))
  int array[] = {23,34,12,17,204,99,16};

  int main()
  {
      int d;
      int x = (TOTAL_ELEMENTS-2);
      for(d=-1;d <= x;d++)
          printf("%d\n",array[d+1]);
      getchar();
      return 0;
  }

我有一个理论，它的东西做的宏，但我不能把我的手指上的问题。

I have a theory that it's something to do with the macro, but I can't put my finger on the problem.

推荐答案

的问题是，（TOTAL_ELEMENTS-2）是一个无符号值。当你作出比较 D＆LT; =（TOTAL_ELEMENTS-2），这两个值被转换为无符号值，其结果是假的。

The problem is that (TOTAL_ELEMENTS-2) is an unsigned value. When you make the comparison d <= (TOTAL_ELEMENTS-2), both values are converted to unsigned values, and the result is false.

在你的第二个例子， X 签订所以没有问题。

In your second example, x is signed so there is no problem.

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