Array to Stack in java , and remove operators

Question

I have one array (25*ax+c-d/2) and i want to put everything in a stack and next remove the operators ( *;+;-;/) and have at the end (25;ax;c;d) in a stack implementation.

Right now i have :

import java.util.*; 
  
public class StackDemo { 
    public static void main(String args[]) 
    { 
      	//Creating array
      	ArrayList<String> al = new ArrayList<String>();
      
      	//Adding to array
      	al.add("25*ax+c-d/2");
      
      	
      	//Creating a stack 
        Stack<String> STACK = new Stack<String>(); 
  
        //Adding array to stack 
        for(String str : al)
  			STACK.add(str);
  
        // Displaying the Stack 
        System.out.println("Initial Stack: " + STACK); 
  
    } 
}

I know I'm grouping everything in the same stack position, but how can I separate and then remove the operators?

Your solution is pretty far away from being functional. As a hint, you can start by writing some logic which can identify one or more tokens which might appear in your algebraic expression. Here, a token means for example a number (e.g. 25) or an operator (e.g. + or -). Then, your code needs to read each token, one at a time, and figure out what to do with them, by putting them on the stack, or doing a math operation. — Tim Biegeleisen
– Tim Biegeleisen, Commented Oct 22, 2019 at 9:54
i dont need to a math operation , i just need to remove the operators of the array and put the result on different positions of the stack. — Pedro Mariz
– Pedro Mariz, Commented Oct 22, 2019 at 10:00
Why? Hard to see the utility of this. Surely at some point you are going to evaluate the expression? Don't design the solution before you fully understand the problem. Hint: Dijkstra Shunting-yard algorithm. — user207421
– user207421, Commented Oct 22, 2019 at 10:04

Hulya · Accepted Answer · 2019-10-22 10:08:30Z

1

You can use regex to split the expression with operators:

public static void main(String[] args) {
    //Creating array
    List<String> al = Arrays.asList("25*ax+c-d/2".split("[\\*+/-]"));

    //Creating a stack 
    Stack<String> STACK = new Stack<String>(); 

    //Adding array to stack 
    for(String str : al)
        STACK.add(str);

    // Displaying the Stack 
    System.out.println("Initial Stack: " + STACK); 
}

Output:

Initial Stack: [25, ax, c, d, 2]

edited Oct 22, 2019 at 10:08

answered Oct 22, 2019 at 10:00

Hulya

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2 Comments

user207421 Over a year ago

The only thing you need to escape here is *.

Hulya Over a year ago

You're right, it should be "[\*+/-]", i'm updating the answer.

Bogdan Kobylynskyi · Accepted Answer · 2021-08-20 21:28:39Z

0

From JavaDoc reference of Stack class:

A more complete and consistent set of LIFO stack operations is provided by the Deque interface and its implementations, which should be used in preference to this class.

Deque<String> stack = new ArrayDeque<String>();

In your scenario, it is possible to initialize a Deque by passing an ArrayList directly:

List<String> al = Arrays.asList("25*ax+c-d/2".split("[\\*+/-]"));
Deque<String> stack = new ArrayDeque<String>(al);

answered Aug 20, 2021 at 21:28

Bogdan Kobylynskyi

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