import java.util.*;

class PostFix {
    public LinkedList<String> inFix;
    public LinkedList<String> postFix;

    public static void main(String[] args) {
        PostFix test = new PostFix();
        test.inFix = new LinkedList<String>();
        test.inFix.add("2.1");
        test.inFix.add("/");
        test.inFix.add("3.2");
        test.inFix.add("-");
        test.inFix.add("(");
        test.inFix.add("6.3");
        test.inFix.add("-");
        test.inFix.add("4.2");
        test.inFix.add(")");

        // === For testing ===
        //while (!test.inFix.isEmpty()) System.out.print(test.inFix.remove());

        test.inFixToPostFix();

        // === For testing ===
        //while (!test.postFix.isEmpty()) System.out.print(test.postFix.remove() + " ");
    }

    public static boolean isoperator(String arg) {
        return arg.equals("+") || arg.equals("-") || arg.equals("*") || arg.equals("/") || arg.equals("(") || arg.equals(")");
    }

    public void inFixToPostFix() {
        if (inFix == null)
            return;

        // create ranking
        HashMap<String, Integer> rank = new HashMap<String, Integer>();
        rank.put("*", 2);
        rank.put("/", 2);
        rank.put("+", 1);
        rank.put("-", 1);

        postFix = new LinkedList<String>();
        LinkedList<String> operatorStack = new LinkedList<String>();

        while (!inFix.isEmpty()) {
            String curr = inFix.remove();

            if (!isoperator(curr))
            {
                postFix.add(curr);
            } else if (curr.equals("(")) {
                operatorStack.push(curr);
            } else if (curr.equals(")")) {
                while (!operatorStack.peek().equals("(")) {
                    postFix.add(operatorStack.pop());
                }
                operatorStack.remove(); // remove "("
            } else { // it's an operator +,-,*,/
                int currRank = rank.get(curr);

                if (!operatorStack.isEmpty() && !operatorStack.peek().equals("(") && rank.get(operatorStack.peek()) >= currRank) {
                    while (!operatorStack.isEmpty() && rank.get(operatorStack.peek()) >= currRank) {
                        postFix.add(operatorStack.pop());
                    }
                }
                operatorStack.add(curr);
            }
        }

        while (!operatorStack.isEmpty()) {
            postFix.add(operatorStack.pop());
        }
    }
}