How to make List random by shuffling-CodePudding

I want to make the quiz randomly generated by shuffling them. I created the shuffle class and call the method to shuffle the sample data. But here is the problem, it didn't display randomly as I wanted. I think I am missing something but I have no idea what did I miss. I have called the shuffle method and print them. Can anyone please enlighten me?

//this is the shuffle method and I call the method to shuffle the sample data

List shuffle(List data) {
  var random = new Random();

  // Go through all elements.
  for (var i = data.length - 1; i > 0; i--) {
    // Pick a pseudorandom number according to the list length
    var n = random.nextInt(i   1);

    List temp = data[i];
    data[i] = data[n];
    data[n] = temp;
  }

  return data;
}

main() {
  print(shuffle(sample_data));
}

//this is the whole page

class Question {
  final int? id, answer;
  final String? question;
  final List<String>? options;
  //final List<String>? audio;

  Question({this.id, this.question, this.answer, this.options});
}

const List sample_data = [
  {
    "id": 1,
    "question": "Apakah maksud waqaf?",
    "options": ['Berhenti', 'Sambung tanpa nafas baru', 'Sambung', 'Dengung'],
    "answer_index": 2,
  },
  {
    "id": 2,
    "question": "Apakah pengertian qalqalah dari segi bahasa? ",
    "options": ['jelas ', 'lantunan ', 'nyata', 'berhenti'],
    "answer_index": 1,
  },
  {
    "id": 3,
    "question": "Qalqalah terbahagi kepada ________ jenis.",
    "options": ['1', '2', '3', '4'],
    "answer_index": 1,
  },
  {
    "id": 4,
    "question":
        "“Pertemuan antara mim sakinah dengan huruf ba dengan dengung 2 harakat”. ",
    "options": [
      'Izhar Halqi',
      'Wajibul Ghunnah',
      'Ikhfa Syafawi',
      'Idgham bila ghunnah'
    ],
    "answer_index": 2,
  },
];
List shuffle(List data) {
  var random = new Random();

  // Go through all elements.
  for (var i = data.length - 1; i > 0; i--) {
    // Pick a pseudorandom number according to the list length
    var n = random.nextInt(i   1);

    List temp = data[i];
    data[i] = data[n];
    data[n] = temp;
  }

  return data;
}

main() {
  print(shuffle(sample_data));
}

CodePudding user response：

Just use list.shuffle(); method

void main() {
   List<Object> myList = ["some", "list", "elements"];
   myList.shuffle();
   print(myList); //["some", "elements", "list"]
}

CodePudding user response：

Something like this?

public class Test {
    private static Random rand = new Random();

    public static <T> void swap(T[] a, int i, int j){
        T temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }

    public static <T> void shuffle(T[] arr) {
        int length = arr.length;
        for ( int i = length; i > 0; i-- ){
            int randInd = rand.nextInt(i);
            swap(arr, randInd, i - 1);
        }
    }

    public static void main(String[] args) {
        Integer[] arr = {1, 2, 3, 4, 5, 6, 7};
        shuffle(arr);
        System.out.println(Arrays.toString(arr));
    }
}

CodePudding user response：

You can use inbuild shuffle() of List

e.g.

 List<String> _str =["1" ,"3" ,"2" ,"5" ,"7"];

 _str.shuffle();