I have the following code:

const arr = Array.from({length: 5}, (_, i) => i + 1);
const finalArray = [];
for (let i = 0; i < arr.length; i++) {
   for (let j = 0; j < arr.length; j++) {
       finalArray.push(arr[i] + '-' + arr[j])


Which creates an array of range 1 => 5, and returns an array with a combination of all elements in the original array.

This code runs in O(n²), is it possible to make it more efficient?

  • 1
    \$\begingroup\$ The current question title, which states your concerns about the code, applies to too many questions on this site to be useful. The site standard is for the title to simply state the task accomplished by the code. Please see How do I ask a good question?. \$\endgroup\$
    – BCdotWEB
    Feb 23, 2021 at 8:35

1 Answer 1



You cannot output \$\Theta(n^2)\$ items in \$o(n^2)\$ time. Output size is a trivial lower bound of any algorithms.

  • \$\begingroup\$ So you mean that my code is most performant? \$\endgroup\$
    – callback
    Feb 23, 2021 at 12:30
  • 1
    \$\begingroup\$ @callback from the view of big-O notation: Yes. To improve its performance: Maybe No. \$\endgroup\$
    – tsh
    Feb 24, 2021 at 1:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.