FAQ: Bubble Sort: JavaScript - Intro to Bubble Sort

Frequently Asked Questions JavaScript FAQ
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This community-built FAQ covers the “Intro to Bubble Sort” exercise from the lesson “Bubble Sort: JavaScript”.

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This exercise can be found in the following Codecademy content:

Pass the Technical Interview with JavaScript

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According to the lesson Bubble Sort’s best-case runtime is O(n) for an already-sorted list. Why not O(N^2), as the two for loops are executed.

Is the swapping section that only matters?

Because we are still checking if the current value > next value?

By the way which instructions are to be analysed for runtime - condition checking, loops, assignment or arithmetic?

I am really confused here. Your suggestions is appreciated.

3

Are there two loops in a bubble sort, or just repetition of one loop while the values bubble up? If the loop only runs once, then, yes, that is the best case, and it would be O(n). It would never be O(n^2) if there is no nested loop, but might as a worst case be something along the lines of O(n log n).

1 Like
4

Thank you mtf for your reply. Here is my code using two for loops, my question was based on this.

const arr = [20, 5, 10, 30, 11, 22, 31];

let temp;

for(let i=0; i < arr.length - 1; i++){
  for(let j=i+1; j < arr.length; j++){
    if(arr[i] > arr[j]){
      temp = arr[i];
      arr[i] = arr[j];
      arr[j] = temp;
    }
  }
}

console.log(arr);

Thank you.

1 Like
5

Because the inner loop is smaller with each pass, the complexity is diminishing. I’m inclined to put this one at O(n log n), but I’ve been wrong before. Let’s wait and see if your post gets more replies.

1 Like