easy

Implement Bubble Sort

Sort an array by repeatedly comparing and swapping adjacent out-of-order pairs.

1. Define the problem

Implement Bubble Sort

Given an integer array nums, sort it in ascending order and return the sorted array. You must sort it using bubble sort : repeatedly walk the array comparing each pair of neighbors, swapping them whenever the left value is bigger than the right one, until a full pass makes no swaps.

Constraints

  • 1 ≤ nums.length ≤ 1000
  • -104 ≤ numsi ≤ 104

Example

Inputnums = [5, 3, 8, 4, 2]
Output[2, 3, 4, 5, 8]

Explanation Repeated adjacent swaps move each value toward its correct spot until the array reads [2, 3, 4, 5, 8].

2. Know the words first

In plain terms

Bubble sort
A sorting technique that repeatedly compares neighboring elements and swaps them when they are out of order, so the largest unsorted value "bubbles" to its final position on each pass.
3. Visualize the solution

Compare and swap neighbors, one pass at a time

Compare and swap neighbors, one pass at a time
Statusstart

Initial array, before any passes: [5, 3, 8, 4, 2].

What happens in this step

[5, 3, 8, 4, 2]

Sorting begins with the full array unsorted; pass 1 will compare each neighbor pair left to right.
Step 1 of 4

Steps to visualize

  1. Walk the array left to right, comparing each pair of adjacent values.
  2. Swap the pair whenever the left value is bigger than the right value.
  3. After a full pass, the largest unsorted value sits at the end — shrink the unsorted region by one.
  4. Repeat until a pass finishes with zero swaps.
4. Walk through the code

Walk through the code

Same walkthrough, now with the code. Press Next to move one step and watch which lines run.

Compare and swap neighbors, one pass at a time
Statusstart

Initial array, before any passes: [5, 3, 8, 4, 2].

What happens in this step

[5, 3, 8, 4, 2]

Sorting begins with the full array unsorted; pass 1 will compare each neighbor pair left to right.
Step 1 of 4
5. Solution

Solution

solution.tsTypeScript
function bubbleSort(nums) {
  const arr = nums.slice();
  const n = arr.length;

  for (let pass = 0; pass < n - 1; pass++) {
    let swapped = false;

    for (let i = 0; i < n - 1 - pass; i++) {
      if (arr[i] > arr[i + 1]) {
        const temp = arr[i];
        arr[i] = arr[i + 1];
        arr[i + 1] = temp;
        swapped = true;
      }
    }

    if (!swapped) break;
  }

  return arr;
}
Time
O(n^2)
Space
O(1)
6. Test cases

Test cases

InputExpectedCovers
nums = [5, 3, 8, 4, 2][2, 3, 4, 5, 8]example from the docstring
nums = [1, 2, 3][1, 2, 3]already sorted, no swaps needed
nums = [5, 4, 3, 2, 1][1, 2, 3, 4, 5]worst case, reverse sorted input
nums = [7][7]smallest valid input, a single element
nums = [3, 1, 3, 2, 1][1, 1, 2, 3, 3]duplicate values scattered through the array
nums = [-2, 5, -1, 0, 3][-2, -1, 0, 3, 5]negative values mixed with positive ones
nums = [4, 4, 4][4, 4, 4]every element is the same value
nums = [2, 1][1, 2]boundary case, exactly two elements out of order

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