Efficient solution to Exercise 2-4

[ChenZhongPu]

squeeze.c is not very efficient. A better way:

void squeeze(char s1[], const char s2[]) {
  int i, j, k;
  int match;

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