Generate 'n' unique random number within a range

Question

I need to generate 5 random number within a specific range from 1 to 100 with out duplicates.

A1 = 1(from)
A2 = 100(to)
A3 = 5 (Required random number)
A4,A5,A6,A7,A8 in cell should generate random number

Answer 1

A simple way could be:

• Generate a list of the 100 numbers
• Shuffle the list using the Fisher-Yates algorithm
• Take the first 5 numbers

There are faster ways, but for only 100 integers it should be fine.

Edit: Try this code:

function shuffleArray(array) { // from http://stackoverflow.com/a/12646864/5710637
    for (var i = array.length - 1; i > 0; i--) {
        var j = Math.floor(Math.random() * (i + 1));
        var temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
    return array;
}

function Randomnumber() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var range = sheet.getRange("c2:C5");
  var min = sheet.getRange("A1").getValue();
  var max = sheet.getRange("A2").getValue();
  var numbers = []
  for (var i = min; i <= max; i++) {
    numbers.push(i);
  }
  shuffleArray(numbers)
  var counter = 0;
  for (var x = 1; x <= range.getWidth(); x++) {
    for (var y = 1; y <= range.getHeight(); y++) {
      range.getCell(y, x).setValue(numbers[counter]);
      counter++;
    }
  }
};

Answer 2

As fafl pointed you can use a list.

• Generate list according to Range
• Pop n Numbers out of them randomly one by one
• Write popped Numbers to sheet

Here is an example.

/*Note: The Code does not have validations like the random number needed should be less
than the range etc. You  should take care of such issues and improvise the code for the
same.
Rest of the code is optimized and makes a single read and write from Spread Making it
run fast*/
function myFunction() {
  //var ss = SpreadsheetApp.getActiveSpreadsheet();
  var ss = SpreadsheetApp.openById("1_xoBxknhDm1pM3MBw0Jbat3BTV4HXep7nZlOPw4tEWg");
  var sheet = ss.getSheets()[0];
  var values = sheet.getRange(1, 2, 3, 1).getValues();
  var nRandomNumbers = getNRandomNumbers(values[0][0], values[1][0], values[2][0]);
  sheet.getRange(4,2,values[2][0],1).setValues(nRandomNumbers);
}
function getRandomNumber(min, max) {
  return Math.random() * (max - min) + min;
}
function getNRandomNumbers(from, to, n){
  var listNumbers = [];
  var nRandomNumbers = [];
  for(var i = from; i <= to; i++) {
    listNumbers.push(i);
  }
  for(var i = 0; i < n; i++) {
    var index = getRandomNumber(0, listNumbers.length);
    nRandomNumbers.push([listNumbers[parseInt(index)]]);
    listNumbers.splice(index, 1);
  }
  return nRandomNumbers;
}

Demo Link:(Please Copy the code into your drive/sheet, can't get the permission working)

Script: https://script.google.com/d/1hsWiGCFZ3DlxiSB3ysTr5ThWvDzThS-vBVzHrJCIEW8zM4_DzndCwGkQ/edit?usp=sharing

Sheet: https://docs.google.com/spreadsheets/d/1_xoBxknhDm1pM3MBw0Jbat3BTV4HXep7nZlOPw4tEWg/edit#gid=0