c - 有关 C 编程语言 (K&R) 的问题 - 练习 1-13

Question

我是编程新手。

我的 C 编程语言 (K&R) 练习 1-13 的解决方案代码中有 6 个问题。任务是编写一个程序来打印单词长度的直方图。如图所示。

我粘贴了下面的代码以及我所做的注释以帮助我理解。

我的问题位于我有疑问的代码的相应部分旁边。提前致谢!

int main ()
{

int c, i, nc, state;
int len;                      /* length of each bar           */
int maxvalue;                 /* maximum value for wl[]       */
int ovflow;                   /* number of overflow words     */
int wl[MAXWORD];              /* word length counters. Defining an int array with 11 character variables. This is the same as saying int wl[11]           */


state = OUT;
nc = 0;                       /* number of chars in a word    */
ovflow = 0;                   /* number of words              */

1. 下面这个 for 循环的目的是什么？它会初始化数组吗？

    for (i = 0; i < MAXWORD; ++i)
      wl[i] = 0;


while ((c = getchar()) != EOF) //get a character
{
  if (c == ' ' || c == '\n' || c == '\t') // if c is a blank, new line or tab
  {
      state = OUT;  // we are outside a word. 

下面，我们有(nc > 0)虽然上面声明了 nc，但 nc 是如何声明的？改变了？比如用户如何更改它？ nc 的输入在哪里？

      if (nc > 0) 

          if (nc < MAXWORD) //if the number of characters is less than the maxword length counter.
          {
              ++wl[nc]; // increase the number of elements/number of characters in the array by 1.  
          }

++wl[nc] 中的增量运算符是什么？增加1？是否增加数组wl ？ nc有什么意义？在++wl[nc] ？

          else
          {
              ++ovflow; // if nc is greater than the maxword however, increase the overflow by 1
          } 

      nc = 0;
  } 

上面，nc = 0重置字符数？

  // The beginning of a new word

  else if (state == OUT) {  //if state is out or better put, if we are not in a word
      state = IN;             // In that case, upon accepting a new character, we are at the start of a new word hence state is in.
      nc = 1;                 // and upon accepting a character, the number of characters is 1.
  }

  // inside a word
  else 
  {
      ++nc;                   // if not outside a word or in a word, increase the number of characters by 1

  }

}

在下面的行中，我们初始化 maxvalue ？

maxvalue = 0 ;
for (i = 1; i < MAXWORD; ++i) //Run a for loop until i is 10. Since MAXWORD length counter is 11.
  {
      if (wl[i] > maxvalue) //if the elements in the array is greater than the max number of elements allowed in the array
              maxvalue = wl[i]; //the max amount of elements allowed in the array is the same as the number of elements in the array. 
      }

我不明白这部分代码。有人可以给我解释一下吗？

for (i = 1; i < MAXWORD; ++i)
{
  printf("%5d - %5d : ", i, wl[i]); //i refers to the word length while wl[i] is the frequency of its occurence.
  if (wl[i] > 0) {
      if ((len = wl[i] * MAXHIST / maxvalue) <= 0)
          len = 1;

  }

  else
      len = 0;
  while (len > 0) 
  {
      putchar ('*');
      --len;

  }
  putchar('\n');

}
if (ovflow > 0)
  printf("There are %d words >= %d\n", ovflow, MAXWORD);

Answer 1

1. 是

2. 更改为else if (state == OUT)

3. wl 数组中的第 nc 元素递增(array[1] 是数组中的第二个元素，因此第 nc 个元素是实际上是 nc + 1...)

4. 是
5. 是
6. for 循环打印单词计数器(是哪个单词)及其长度。

如果特定单词的长度大于 0，则 len 获取值 wl[i] * MAXHIST/maxvalue，然后检查 0。如果它等于 0，则 len 变为 1。

否则:len 变为 1

在这之后，程序打印 len 次 '*'，然后是换行符