package guava;

import java.util.Stack;

/**
 *
 * @author rtibbetts268
 */
public class ThrowablesPlayground
{

	public static void main(String[] args) {
		System.out.println(new ThrowablesPlayground().convert2Postfix("-4"));
	}
        /**
         * Operators in reverse order of precedence.
         */
    private static final String operators = "_-+/*";
    private static final String operands = "0123456789x";

    public String convert2Postfix(String infixExpr){
        char[] chars = infixExpr.toCharArray();
        StringBuilder in = new StringBuilder();
        for (int i=0;i<chars.length;++i){
            if (infixExpr.charAt(i) == '-'){
                if (isOperand(infixExpr.charAt(i+1))){
                    if (i != infixExpr.length()){
                        if (isOperator(infixExpr.charAt(i))) {
                        	in.append('_');
                        }
                    }
                    else{
                        in.append(infixExpr.charAt(i));
                    }
                }
                else{
                   in.append(infixExpr.charAt(i));
                }
            }
            else{
                in.append(infixExpr.charAt(i));
            }
        }

        chars = in.toString().toCharArray();
        Stack<Character> stack = new Stack<Character>();
        StringBuilder out = new StringBuilder();
        for (char c : chars){
            if (isOperator(c)){
                while (!stack.isEmpty() && stack.peek() != '('){
                    if (operatorGreaterOrEqual(stack.peek(), c)){
                        out.append(stack.pop());
                    }
                    else{
                        break;
                    }
                }
                stack.push(c);
            }
            else if (c == '('){
                stack.push(c);
            }
            else if (c == ')'){
                while (!stack.isEmpty() && stack.peek() != '(')
                {
                    out.append(stack.pop());
                }
                if (!stack.isEmpty())
                {
                    stack.pop();
                }
            }
            else if (isOperand(c)){
            	System.out.println("33333="+c);
                out.append(c);
            }
        }
        while (!stack.empty()){
            out.append(stack.pop());
        }
        return out.reverse().toString();
    }

    public int evaluatePostfix(String postfixExpr)
    {
        char[] chars = postfixExpr.toCharArray();
        Stack<Integer> stack = new Stack<Integer>();
        for (char c : chars)
        {
            if (isOperand(c))
            {
                stack.push(c - '0'); // convert char to int val
            }
            else if (isOperator(c))
            {
                int op1 = stack.pop();
                int op2 = stack.pop();
                int result;
                switch (c) {
                    case '*':
                        result = op1 * op2;
                        stack.push(result);
                        break;
                    case '/':
                        result = op2 / op1;
                        stack.push(result);
                        break;
                    case '+':
                        result = op1 + op2;
                        stack.push(result);
                        break;
                    case '-':
                        result = op2 - op1;
                        stack.push(result);
                        break;
                }
            }
        }
        return stack.pop();
    }

    private int getPrecedence(char operator)
    {
        int ret = 0;
        if (operator == '_')
        {
            ret = 0;
        }
        if (operator == '-' || operator == '+')
        {
            ret = 1;
        }
        else if (operator == '*' || operator == '/')
        {
            ret = 2;
        }
        return ret;
    }

    private boolean operatorGreaterOrEqual(char op1, char op2)
    {
        return getPrecedence(op1) >= getPrecedence(op2);
    }

    private boolean isOperator(char val)
    {
        return operators.indexOf(val) >= 0;
    }

    private boolean isOperand(char val)
    {
        return operands.indexOf(val) >= 0;
    }

}