Question 49550 in Javascript Question posted in
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Javascript math.random gives too many duplicate values

Using NodeJS 14. I have a script that needs to generate 10,000 unique numbers between 1 and 10000. i have a function that takes 1 as min and 10000 as max. When I run it, only ~7000 are unique the rest are duplicates. I understand that not all 10k would be unique, but 30%? What can I do to get more of then unique?

function is:

function getRandomInt(min, max) {
    min = Math.ceil(min);
    max = Math.floor(max);
    return Math.floor(Math.random() * (max - min + 1)) + min;
}

sorted sample
1856
1871
1873
1879
1879
1885
1895
1903
1911
1911

Tags:

2

Answers


  1. 0

    To obtain exactly 10000 unique random numbers, you can just shuffle all the integers from 1 to 10000.

    let nums = Array.from({length:10000}, (_, i) => i + 1);
for (let i = nums.length - 1; i > 0; i--) {
  const j = Math.random() * (i + 1) | 0;
  [nums[i], nums[j]] = [nums[j], nums[i]];
}
console.log(nums);
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  2. 0

    You can loop through the size of the set an keep pushing into it until the size if your desired size. Set guarantees uniquness.

    const uniqueNumbers = new Set(); 

while (uniqueNumbers.size < 10000) { 
  let randomNum = Math.floor(Math.random() * 10000) + 1; 
  uniqueNumbers.add(randomNum); 
}

//set to array
console.log([...uniqueNumbers]);
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