Random generator without repeated result

I need to put the numbers from low to high in an array randomly.

low

high

For example given: low = 10, high = 15 a result like [ 12, 13, 10, 14, 11] is good.

[ 12, 13, 10, 14, 11]

This is a simple algorithm: iterate from low to high and try to fill in the empty slots on an array.

const low = 1000
const high = 1010

const diff = high - low
const arr = new Array(diff)

for (var i = low; i < high; i++) {
let success = false
while(!success) {
const index = Math.floor(Math.random() * diff)
if (arr[index] === undefined) {
arr[index] = i
success = true
}
console.log(`${index} was ${success ? 'available' : 'taken'}`)
}
}

console.log(arr)

The problem is: in the end where most of the elements are filled, it is harder to find an unoccupied slot in the array.

My question is: is there an algorithm that constantly generates unique new numbers until all the numbers are consumed?

1 Answer
1

Instead of generating "random" numbers, generate a list of the numbers and shuffle it "randomly" by using something like Fisher-Yates Shuffle:

function getRandomArray(min, max) {
var arr = ;
for (var i = min; i < max; i++) {
arr.push(i);
}

return arr;
}

function shuffle(array) {
var m = array.length, t, i;

while (m) {

i = Math.floor(Math.random() * m--);

t = array[m];
array[m] = array[i];
array[i] = t;
}

return array;
}

var randomArr = getRandomArray(10, 15);
shuffle(randomArr);
console.log(randomArr);


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