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Android - calculating and storing the answer of an arithmetic expression



What would be best way to get the answer to this question which is using random numbers and random operators.







editTextEquation.setText(random1 +(String.valueOf(ops[i1]) + random2 + (String.valueOf(ops[i2])+ random3 + (String.valueOf(ops[i3])+ random4))));







I'm displaying this question and then will check the answer against user input. I'm guessing I'd need to store the answer first. Any help/advice will be very much appreciated.





Here is how I am generating the expression:







int random1 = (int)(Math.random()*100);

int random2 = (int)(Math.random()*100);

int random3 = (int)(Math.random()*200);

int random4 = (int)(Math.random()*20);



int min = 0;

int max = 3;

Random r = new Random();

int i1 = r.nextInt(max - min);

int i2 = r.nextInt(max - min);

int i3 = r.nextInt(max - min);



char[] ops = { '+', '-', '/', '*' };



int answer;




Comments

  1. How long do you need to hold on to the answer?

    If it's only for a short time, a variable will be sufficient.

    If you need it for a long time, consider creating a SQLite database to store it. Generate an ID for your expression and store them both in the database. Then you can look them up later at your leisure.

    ReplyDelete
  2. If you only have small problems, so only a couple of + and - etc, you could try creating a string to represent it, and an underlying operation to find the answer, for example

    public int calculate(int operation, int a, int b, int c) {
    if (operation ==1) {
    //must be all plus
    return a+b+c;
    }else if (operation ==2)
    //another case
    return a+b-c;
    }else if ( etc etc

    }

    public void displayQuestion(int operation, int a, int b, int c) {
    if(operation ==1) {
    System.out.println(a + " + " + b + " + " + c + " =");
    }else if( etc etc
    }


    You could then display each question and request the answer depending on what it was. This is a simple way that will require you having every case specified. You can probably easily make it alot smarter, this is a quick simple way, to do it properly (parse the string as a math query) is a bit harder and I need to get back to my actual work!

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