ex8_04.c

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/* Exercise 8.4 A function to return the number of words in a string passed as an argument */
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

#define LENGTH_INCREMENT  20
#define MAX_WORD_LENGTH   30

int countwords(char str[]);                                    /* Function to count words in a string */
int segment_string(char str[], char *words[]);                 /* Function to segment a string        */
int count_letters(char str[]);                                 /* Function to count letters in a word */


int main(void)
{
   char* pStr = NULL;             /* Points to memory that stores the string */
   char* pTemp = NULL;            /* Temporary pointer                       */
   char** words = NULL;           /* Pointer to an array of words            */
   int length = 0;                /* Current string length                   */
   int max_length = 0;            /* Current maximum string length           */
   int wordcount = 0;             /* Count of words in string                */

   /* Read the string */
   printf("Enter a string:\n");
   do
   { /* If there is not enough memory, allocate some more */
     if(length >= max_length)
     {
       max_length += LENGTH_INCREMENT;
       pTemp = (char*)malloc(max_length);
       if(pStr)          /* If we have already read characters */
       {                 /* copy them to the new memory        */
         for(int i = 0 ; i<length ; i++)
           pTemp[i] = pStr[i];
         free(pStr);
       }
       pStr = pTemp;
       pTemp = NULL;
     }
   }while((pStr[length++] = getchar()) != '\n');
   pStr[--length] = '\0';         /* Append string terminator */

   wordcount = countwords(pStr);  /* Get the word count       */

   /* Now allocate memory to hold the words */
   words = (char**)malloc(wordcount*sizeof(char*));
   for(int i = 0 ; i<wordcount ; i++)
     words[i] = (char*)malloc(MAX_WORD_LENGTH);

   segment_string(pStr, words);   /* Segment the string into words */

   /* Sort the words in order of length */
   for(int i = 0 ; i<wordcount-1 ; i++)
     for(int j = i ; j<wordcount ; j++)
       if(count_letters(words[i]) > count_letters(words[j]))
       {
         pTemp = words[i];
         words[i] = words[j];
         words[j] = pTemp;
       }
   /* Output the words and free the memory */
   printf("The words in the string in order of length are:\n");
   for(int i = 0 ; i<wordcount ; i++)
   {
     printf("%s\n",words[i]);
     free(words[i]);
   }
   free(words);      /* Free the memory for the pointers */
   return 0;
}

/* Function to count words in a string */
int countwords(char str[])
{
  int count = 0;
  int i = 0;
  while(str[i] != '\0')
  {
    if(!isalpha(str[i]))
    {
      i++;
      continue;
    }
    ++count;
    while(isalpha(str[++i]))
      ;
  }
  return count;
}

/* Function to segment a string into words and return he number of words */
int segment_string(char str[], char *words[])
{
  int count = 0;
  int i = 0;
  int j = 0;
  while(str[i] != '\0')
  {
    if(!isalpha(str[i]))
    {
      i++;
      continue;
    }
    j = 0;
    while(isalpha(str[i]))
    {
      words[count][j++] = str[i++];
    }
    words[count++][j] = '\0';
  }
 return count;
}

/* Function to count letters in a word */
int count_letters(char str[])
{
  int count = 0;
  int i = 0;
  while(str[i] != '\0')
  {
    if(isalpha(str[i++]))
      ++count;
  }
  return count;
}