get Inverse Poland Expression - Java Data Structure

Java examples for Data Structure:Inverse Poland Expression

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Description

get Inverse Poland Expression

Demo Code


//package com.java2s;
import java.util.ArrayList;
import java.util.List;

import java.util.Stack;

public class Main {
    public static void main(String[] argv) throws Exception {
        String normalExpression = "java2s.com";
        System.out.println(getInversePolandExpression(normalExpression));
    }//  w w  w  . jav  a  2s  . c  om

    static private List<String> getInversePolandExpression(
            String normalExpression) {
        List<String> inversePolandExpression = new ArrayList<String>();
        char[] normalChararray = (normalExpression + "$").toCharArray();
        // 
        Stack<String> signStack = new Stack<String>();
        List<Stack<String>> signStackList = new ArrayList<Stack<String>>();
        signStackList.add(signStack);
        // 
        int level = 0;

        int pointPosition = 0;
        double tempNumber = 0;
        boolean isInInteger = true;

        for (int i = 0; i < normalChararray.length; i++) {
            char tempChar = normalChararray[i];
            // 
            if (tempChar >= '0' && tempChar <= '9') {
                // 
                if (isInInteger) {
                    tempNumber = tempNumber * 10 + (int) (tempChar - 48);
                }
                // ?
                else {
                    tempNumber += (double) (tempChar - 48)
                            * Math.pow(0.1, i - pointPosition);
                }

            }
            // ?
            else if (tempChar == '.') {
                isInInteger = false;
                pointPosition = i;
            }
            // 
            else if (tempChar == '+' || tempChar == '-' || tempChar == '*'
                    || tempChar == '/' || tempChar == '$') {
                // 
                isInInteger = true;
                // ?
                if (tempNumber > 0) {
                    inversePolandExpression.add(String.valueOf(tempNumber));
                }
                // 0
                tempNumber = 0;
                // ???
                if ((tempChar == '+') || (tempChar == '-')
                        || tempChar == '$') {

                    while (!signStackList.get(level).isEmpty()) {
                        // 
                        inversePolandExpression.add(signStackList
                                .get(level).pop());
                    }
                }
                // ?

                signStackList.get(level).push(tempChar + "");

            } else if (tempChar == '(') {
                signStack = new Stack<String>();
                signStackList.add(signStack);
                level++;
            } else if (tempChar == ')') {
                // 
                isInInteger = true;
                // ?
                if (tempNumber > 0) {
                    inversePolandExpression.add(String.valueOf(tempNumber));
                }

                // 0
                tempNumber = 0;
                // ???

                while (!signStackList.get(level).isEmpty()) {
                    // 
                    inversePolandExpression.add(signStackList.get(level)
                            .pop());

                }
                level--;
            }
        }
        return inversePolandExpression;
    }
}

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