Kotlin中的冒泡排序

1. Overview

In this tutorial, we’ll implement the bubble sort algorithm in Kotlin. Being one of the simplest algorithms, bubble sort repeatedly steps through a given list and compares its adjacent elements, and swaps them if they are arranged in the wrong order until the list is sorted. It’s among the most suitable algorithms for small datasets.

2. The Steps of Performing a Bubble Sort

Let’s review the steps involved in performing a Bubble Sort:

• Start with an unsorted list of elements
• Compare the first element with the second element. If the first element is greater than the second element, swap them.
• Move to the next pair of elements and compare them. Repeat this process until you reach the end of the list.
• By the end of the first pass, the largest element will be at the end of the list.
• Repeat steps 2-4 for the remaining elements, excluding the last element. This is because it is already sorted after the first pass.
• Repeat this process until all elements are sorted and no more swaps are needed.

3. Implementation of Bubble Sort Algorithm

Let’s see an example Bubble Sort implementation in Kotlin:

fun bubbleSort(arr: IntArray) {
    val n = arr.size

    for (i in 0 until n - 1) {
        for (j in 0 until n - i - 1) {
            if (arr[j] > arr[j + 1]) {
                // Swap the elements
                val temp = arr[j]
                arr[j] = arr[j + 1]
                arr[j + 1] = temp
            }
        }
    }
}

This code sorts a list of elements and arranges them in ascending order. To use the bubbleSort() function, we can pass an IntArray with our unsorted elements. After the code compiles, the array will be sorted in ascending order.

Let’s see it in action:

val arr = intArrayOf(64, 34, 25, 12, 22, 11, 90)
val expected = intArrayOf(11, 12, 22, 25, 34, 64, 90)
bubbleSort(arr)
assertArrayEquals(expected, arr)

3.1. Sort in Descending Order

Let’s now use the same bubble sort algorithm to sort elements in a list in descending order:

fun bubbleSortDescending(arr: IntArray) {
    val n = arr.size
    for (i in 0 until n - 1) {
        for (j in 0 until n - i - 1) {
            if (arr[j] < arr[j + 1]) {
                val temp = arr[j]
                arr[j] = arr[j + 1]
                arr[j + 1] = temp
            }
        }
    }
}

4. Analysis of Bubble Sort Algorithm

Bubble Sort is a simple comparison-based sorting algorithm. Let’s look at a few of its key characteristics:

In terms of time complexity, bubble sort can be analyzed as best-case time complexity O(n), average-case time complexity O(n^2), and worst-case time complexity O(n^2). This is because the normal bubble sort iterates through a list of elements and sorts them, as we discussed earlier. However, in an average and worst-case scenario, bubble sorting may require multiple passes to sort elements in a list.

Bubble sort has a space complexity of O(1) because it doesn’t need any additional data structures or memory allocation proportional to the input size. The sorting is usually done in place by just swapping the adjacent elements.

Bubble sort isn’t regarded as an adaptive sorting algorithm. This is because it doesn’t take advantage of any pre-existing order in the list. Regardless of the initial order, bubble sort performs the same number of comparisons and swaps for a given list size.

Bubble sort is often used as a teaching tool or for educational purposes due to its simplicity and ease of implementation. However, for practical applications, more efficient sorting algorithms such as quicksort or merge sort are preferred.

4.1. Cons of Bubble Sort

• The bubble sort algorithm is inefficient for large datasets.
• Bubble Sort’s performance is suboptimal as compared to more advanced sorting algorithms like quick sort and merge sort.

5. Conclusion

In this article, we’ve discussed the bubble sort algorithm in Kotlin. We went through the implementation of bubble sort for both the ascending and descending order and the analysis of bubble sort, including its cons.

The full implementation of this code can be found over on GitHub.