Exercises from Chapter 4
                  
4.14
4.19
4.20

                                   Solutions

4.14 
bool palin() {
  Stack<char> S;
  Queue<char> Q;

  while ((c = getc()) != ENDOFSTRING) {
    S.push(c);
    Q.enqueue(c);
  }
  while (!S.isEmpty()) {
    if (S.top() != Q.front()) return FALSE;
    char dum = S.pop;
    dum = Q.dequeue();
  }
  return TRUE;

4.19 As we will learn, using certain kinds of binary tree structures will
permit both insert and find operations to run in time Theta(log n).

4.20 (a)
     bool balance(String str) {
       Stack S<char>;
       int pos = 0;
       while (str.charAt(pos) != NULL) {
         if (str.charAt(pos++) == '(')
           S.push('(');
         else if (str.charAt(pos++) == ')')
           if (S.isEmpty()) return FALSE;
           else S.pop();
       }
       if (S.isEmpty()) return TRUE;
       else return FALSE;
     }
     (b)
     int balance(String str) {
       Stack S<int>;
       int pos = 0;
       while (str.charAt(pos) != NULL) {
         if (str.charAt(pos++) == '(')
           S.push(pos);
         else if (str.charAt(pos++) == ')')
           if (S.isEmpty()) return pos;
           else S.pop();
       }
       if (S.isEmpty()) return -1;
       else return S.pop();
     }