How to generate unique random numbers in flutter and if same are generated how to reassign State

Question

I am beginner in flutter. I am trying to make simple addition program which will generate random number to add with each other and also create 4 random options for answer out of which one will be correct answer. But the problem is sometimes similar options and I don't want to correct options for result.

Below is my code. can anybody help me out?

class _StartGameState extends State<StartGame> {
  int inp1, inp2;
  GenerateQuestion g = new GenerateQuestion();
  int num1, num2, num3, num4;
  int no1, no2, no3, no4;
  int pos;
  int res;
  Map answers;
  bool flag = true;

  void getNum() {
    num1 = g.generateNum();
    num2 = g.generateNum();
    num3 = g.generateNum();
    num4 = g.generateNum();
    inp1 = g.generateValue();
    inp2 = g.generateValue();
    // this method returns value from 0 to 3
    pos = g.answerPosition();
    res = inp1 + inp2;
    switch (pos) {
      case 0:
        num1 = res;
        break;
      case 1:
        num2 = res;
        break;
      case 2:
        num3 = res;
        break;
      case 3:
        num4 = res;
        break;
    }
    if (res == num1 || res == num2 || res == num3 || res == num4) {
      if (num1 != num2 &&
          num1 != num3 &&
          num1 != num4 &&
          num2 != num3 &&
          num2 != num4 &&
          num3 != num4) {
        setState(() {
          no1 = num1;
          no2 = num2;
          no3 = num3;
          no4 = num4;
        });
      }
    }
  }
}

GenerateQuestion is a separate class file. which has simple methods which creates random object with range and returns value;

My Interface is like enter image description here

I don't understand "But the problem is sometimes similar options and I don't want to correct options for result.". Can you try clarify what the issue is? Also, you code can be made a lot simpler but I need to know what the expected behavior should be. — julemand101
– julemand101, Commented Nov 16, 2020 at 18:04
I need 4 unique options as a answer for addition. but random() returns sometimes two similar integers because the range is only upto 20. so for example if my question is 10 + 5 = ? I want answers options i.e, num1, num2, num3, num4 as may be 10, 15, 20, 18. but sometimes i am getting options like , 10, 15, 15, 20. Here 15 is correct answer. but as two options are generated for correct answer(15) user might get confuse which one to select. for that i need unqiue options and one of them should be result of addition. — Dhananjay Gavali
– Dhananjay Gavali, Commented Nov 16, 2020 at 18:06
You mean equal integers? Similar should not be a problem as long it is not the same as another value? — julemand101
– julemand101, Commented Nov 16, 2020 at 18:09
Yes equal integers. I don't want to equal integers for correct answer — Dhananjay Gavali
– Dhananjay Gavali, Commented Nov 16, 2020 at 18:10
I have this kind of interface i.sstatic.net/VrN5Y.png where the four boxes are options for the question. — Dhananjay Gavali
– Dhananjay Gavali, Commented Nov 16, 2020 at 18:12

Asad Jivani · Accepted Answer · 2020-11-16 18:24:35Z

1

In order to make sure that options don't get repeat, you have to validate an option after generating it with already generated options for e.g,

//create a list to store options
var optionList = new List(4);
while(optionList.length() < 4){
  // generate your option
  int option = g.generateNum();
  if(!optionList.contains(option)){
      optionList.add(option);
   }
}
// then get your options
num1 = optionList[0];
num2 = optionList[1];
num3 = optionList[2];
num4 = optionList[3];

edited Nov 16, 2020 at 18:24

answered Nov 16, 2020 at 18:14

Asad Jivani

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Comments

julemand101 · Accepted Answer · 2020-11-16 18:39:09Z

1

I have made the following example which shows how you can generate your options:

import 'dart:math';

void main() {
  final options = getOptions(15, 0, 20, 4);

  final num1 = options[0];
  final num2 = options[1];
  final num3 = options[2];
  final num4 = options[3];

  print('num1: $num1'); // num1: 17
  print('num2: $num2'); // num2: 15
  print('num3: $num3'); // num3: 5
  print('num4: $num4'); // num4: 0
}

List<int> getOptions(int answer, int min, int max, int numberOfOptions) {
  final rnd = Random();
  final options = {answer};

  while (options.length < numberOfOptions) {
    options.add(min + rnd.nextInt(max - min));
  }

  return options.toList()..shuffle();
}

The list of possible generated values will be including min but excluding max.

edited Nov 16, 2020 at 18:39

answered Nov 16, 2020 at 18:33

julemand101

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