java2-home3.java

java2-home3.java

public class Answer {


   public static void main (String[] argum) {
      Answer answer = new Answer();
   }
	
   class Linked {
	   public int value;
	   public Linked parent;
	   
	   Linked(int value, Linked parent) {
		   this.value = value;
		   this.parent = parent;
	   }
	   
	   public boolean equals (Linked o) {
		   if(o==null) return false;
		   if(this.value!=o.value) return false;
		   if(this.parent==o.parent) return true;
		   if(this.parent!=null && o.parent!=null && this.parent.equals(o.parent)) return true;
		   return false;
	   }
	   
	   public Linked clone () {
		   if(this.parent!=null) {
			   return new Linked(this.value, this.parent.clone());
		   } else {
			   return new Linked(this.value, null);
		   }
	   }
	   
	   public String toString() {
		   StringBuffer sb = new StringBuffer();		   
		   if(this.parent!=null) sb.append(this.parent.toString() + " ");
		   sb.append(this.value);

		   return sb.toString();
	   }
	   
   }
   
   public Linked last;

   Answer() {
   }
   
   Answer(Linked last) {
	   this.last = last;
   }

   @Override
   public Object clone() throws CloneNotSupportedException {
      return new Answer(last.clone());
   }

   public boolean stEmpty() {
	   if(null==last) {
		   return true;
	   } else {
		   return false;
	   }
   }

   public void push (int a) {
	   last = new Linked(a, last);
   }

   public int pop() {
      Linked popped = last;
      last = popped.parent;
      return popped.value;
   }

   public void op (String s) {
	  int b = this.pop();
	  int a = this.pop();
	 
	  if(s.equals("+")){ this.push(a+b); }
	  else if(s.equals("-")){ this.push(a-b); }
	  else if(s.equals("*")){ this.push(a*b); }
	  else if(s.equals("/")){ this.push(a/b); }
	  else{ throw new RuntimeException("unknown character: '"+s+"'"); }
   }
  
   public int tos() {
      return last.value;
   }

   @Override
   public boolean equals (Object o) {
	   if(o==null) return false;
	   Answer other = (Answer)o;
	   if(this.last==other.last) return true;
	   if(this.last==null || other.last==null) return false;
	   return this.last.equals(other.last);
   }

   @Override
   public String toString() {
	   if(this.last==null) return "";
	   return this.last.toString();
   }

   public static int interpret (String pol) {
	   pol = pol.replaceAll("\t", " ");
	   pol = pol.replaceAll(" +", " ").trim();
	   
	   String[] elements = pol.split(" ");
	   Answer a = new Answer();
	   
	   for(String e : elements){
		   System.out.println("element: '" + e + "'");
		   try {
			   int value = Integer.parseInt(e);
			   a.push(value);
		   } catch(Exception exception) {
			   a.op(e);
		   }
	   }
	   
	   if(a.last!=null && a.last.parent==null){
		   return a.last.value;
	   } else {
		   throw new RuntimeException("dont match");
	   }
   }

}

// for tests to pass
class Aout {
	public static String toString(String s){
		System.out.println(s);
		return s;
	}
}