How to write a selection sort algorithm in Python?

How to write a selection sort algorithm in Python?

Selection sort is a simple and intuitive sorting algorithm. Its basic idea is to find the smallest element and put it at the end of the sorted part, and then continue to find the smallest element from the unsorted part and repeat the process. Until the entire array is sorted.

Let’s take a closer look at how to write a selection sort algorithm in Python.

First, we define a function select_sort to implement selection sorting. This function receives an array as a parameter and sorts the original array. Two nested loops are used inside the function, the outer loop is used to traverse the array, and the inner loop is used to find the index of the smallest element in the unsorted part.

The code is as follows:

def select_sort(arr):
    n = len(arr)
    for i in range(n-1):
        min_index = i
        for j in range(i+1, n):
            if arr[j] < arr[min_index]:
                min_index = j
        arr[i], arr[min_index] = arr[min_index], arr[i]

Next, we can test the effect of the selection sorting algorithm. For example, sorting an integer array:

arr = [64, 25, 12, 22, 11]
select_sort(arr)
print("排序后的数组：")
for i in range(len(arr)):
    print("%d" % arr[i])

The running results are as follows:

排序后的数组：
11
12
22
25
64

It can be seen that the selection sort algorithm successfully sorts the input array in ascending order.

The time complexity of the selection sort algorithm is O(n^2). Regardless of the input data, its time complexity is the same. Therefore, in practical applications, the selection sort algorithm has low efficiency and is not suitable for sorting tasks of processing large-scale data.

To sum up, this article introduces how to write a selection sort algorithm in Python and gives specific code examples. I hope that readers can master the basic principles and implementation methods of the selection sort algorithm by reading this article, and be able to flexibly apply it to practical problems.

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