How to get a random number without duplicate digits in JavaScript/jQuery?

Question

Update: The number can be started with zero.

I want to have a function like

function getRandomNumber(n){
  ...
}

I hope it gets a number with n digits while none of the digits is repeated. For instance:

getRandomNumber(3) -> 152 is what I want.
getRandomNumber(1) -> 6 is what I want.
getRandomNumber(6) -> 021598 is what I want. It can start with zero.
getRandomNumber(5) -> 23156 is what I want.
getRandomNumber(3) -> 252 is not because it has two 2.
getRandomNumber(5) -> 23153 is not because it has two 3.

Any simple way to do this?

CertainPerformance · Accepted Answer · 2018-04-28 05:15:41Z

1

On each call, make an array of digits, and then repeatedly pick random values and remove them from said array:

function getRandomNumber(n){
  const digits = Array.from({ length: 10 }, (_, i) => i);
  const result = Array.from({ length: n }, () => {
    const randIndex = Math.floor(Math.random() * digits.length);
    const digit = digits[randIndex];
    digits.splice(randIndex, 1);
    return digit;
  });
  return Number(result.join(''));
}


Array.from({ length: 10 }, () => console.log(getRandomNumber(8)));

edited Apr 28, 2018 at 5:15

answered Apr 28, 2018 at 5:11

CertainPerformance

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vibhor1997a Over a year ago

Wow, Amazing solution! It returns a string so please return Number(result.join()).

Redu · Accepted Answer · 2018-04-28 08:33:42Z

1

By keeping an array as an hash map, an efficient solution is as follows. However keep in mind that unless it's a string a number can not start with 0.

function getRandomNumber(n){
    var a = [],
        x = ~~(Math.random()*10),
        r = 0;
    while (n) {
      a[x] === void 0 && (a[x] = true, r += x*Math.pow(10,n-1), --n);
      x = ~~(Math.random()*10);
    }
    return r;
}

console.log(getRandomNumber(3));
console.log(getRandomNumber(4));
console.log(getRandomNumber(5));
console.log(getRandomNumber(6));
console.log(getRandomNumber(7));

edited Apr 28, 2018 at 8:33

answered Apr 28, 2018 at 8:30

Redu

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Redu Over a year ago

~~ a shortcut for Math.floor() for positive real numbers.

KyBe · Accepted Answer · 2018-04-28 05:54:02Z

0

Don't how to deal with javascript but if it can help you, here a line of scala doing the job

def obtainRestrictedRandomNumber(): Long = scala.util.Random.shuffle((0 to 9)).mkString("").toLong

What it does is simply generating all digits from 0 to 9 then randomize them, concatenate the Array Int elements into a string for finally casting it into a Long.

answered Apr 28, 2018 at 5:54

KyBe

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