K&R Exercise 1.9 Replace multiple blank with single blank

Problem Statement

Exercise 1-9: Write a program to copy its input to its output, replacing each string of one or more blanks by a single blank.

Solution

I am assuming that blanks are represented by ' '. It can be easily extended to remove '\t' too.

Strategy

• First loop that takes character using getchar() till EOF.
• Present variable that is got from getchar() is stored in c.
• Since we need to remove continuous space, lets save the previous character in variable old_c.
• When previous character is blank and present character is not a blank, then we will print using putchar both blank and present character.
• If the present character is not blank then we will print it as usual.
• End of the loop present character is assigned to old_c.

C implementation will look as follows-

#include <stdio.h>
int main()
{
   int c;  /* Present Charecter */
   int old_c; /* Previous Charecter */

   while((c = getchar()) != EOF) {
      if(old_c == ' ' && c != ' '){
         putchar(' ');
         putchar(c);
      }else if(c != ' '){
         putchar(c);
      }
      old_c = c;
   }
   return 0;
}

Output
using the file redirection operation

$ cat text 
This is very    long             line.
$ ./e_1_09.out < text 
This is very long line.

Links

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