From clc-wiki

The C Programming Language, 2nd Edition, by Kernighan and Ritchie
Exercise 2.04 on page 48

Write an alternate version of squeeze(s1,s2) that deletes each character in the string s1 that matches any character in the string s2 .

Solution by Richard Heathfield

/*
 * Exercise 2-4 Page 48
 *
 * Write an alternate version of squeeze(s1,s2) that deletes each
 * character in s1 that matches any character in the string s2.
 *
 */

/* squeeze2: delete all characters occurring in s2 from string s1. */

void squeeze2(char s1[], char s2[])
{
  int i, j, k;
  int instr2 = 0;

  for(i = j = 0; s1[i] != '\0'; i++)
  {
    instr2 = 0;
    for(k = 0; s2[k] != '\0' && !instr2; k++)
    {
      if(s2[k] == s1[i])
      {
        instr2 = 1;
      }
    } 

    if(!instr2)
    {
      s1[j++] = s1[i];
    } 
  }
  s1[j] = '\0';
}

/* test driver */

#include <stdio.h>
#include <string.h>

int main(void)
{
  char *leftstr[] =
  {
    "",
    "a",
    "antidisestablishmentarianism",
    "beautifications",
    "characteristically",
    "deterministically",
    "electroencephalography",
    "familiarisation",
    "gastrointestinal",
    "heterogeneousness",
    "incomprehensibility",
    "justifications",
    "knowledgeable",
    "lexicographically",
    "microarchitectures",
    "nondeterministically",
    "organizationally",
    "phenomenologically",
    "quantifications",
    "representationally",
    "straightforwardness",
    "telecommunications",
    "uncontrollability",
    "vulnerabilities",
    "wholeheartedly",
    "xylophonically", /* if there is such a word :-) */
    "youthfulness",
    "zoologically"
  };
  char *rightstr[] =
  {
    "",
    "a",
    "the",
    "quick",
    "brown",
    "dog",
    "jumps",
    "over",
    "lazy",
    "fox",
    "get",
    "rid",
    "of",
    "windows",
    "and",
    "install",
    "linux"
  };

  char buffer[32];
  size_t numlefts = sizeof leftstr / sizeof leftstr[0];
  size_t numrights = sizeof rightstr / sizeof rightstr[0];
  size_t left = 0;
  size_t right = 0;

  for(left = 0; left < numlefts; left++)
  {
    for(right = 0; right < numrights; right++)
    {
      strcpy(buffer, leftstr[left]);

      squeeze2(buffer, rightstr[right]);

      printf("[%s] - [%s] = [%s]\n", leftstr[left], rightstr[right], buffer);
    }
  }
  return 0;
}