trim-space.c

/* Copyright © 2021-2023 Chee Bin HOH. All rights reserved.
 *
 * It trims trailing space or tab at the end of line or file.
 */

#include <ctype.h>
#include <stdio.h>

struct Token {
  char ch;
  long count;
};

int main(int argc, char *argv[]) {
  int c;
  int i;
  int j;
  int tokenIndex;
  int numOfNewLine;
  struct Token tokenList[100];

  tokenIndex = 0;
  numOfNewLine = 0;
  while ((c = getchar()) != EOF) {
    if (isspace(c)) {
      if ('\n' == c) {
        if (numOfNewLine <= 0)
          putchar(c);

        tokenIndex = 0;

        numOfNewLine++;
      } else {
        if (tokenIndex <= 0 || tokenList[tokenIndex - 1].ch != c) {
          tokenList[tokenIndex].ch = c;
          tokenList[tokenIndex].count = 1;

          tokenIndex++;
        } else {
          tokenList[tokenIndex - 1].count++;
        }
      }
    } else {
      while (numOfNewLine > 1) {
        putchar('\n');

        numOfNewLine--;
      }

      for (i = 0; i < tokenIndex; i++) {
        for (j = 0; j < tokenList[i].count; j++) {
          putchar(tokenList[i].ch);
        }
      }

      tokenIndex = 0;
      numOfNewLine = 0;

      putchar(c);
    }
  }

  return 0;
}