问题

我尝试编写一个名为modified_selection_sort的函数，它以一个整数值列表作为参数，并将其按升序排序。该函数应该首先将最大的元素交换到最后一个位置，然后将第二大的元素交换到倒数第二个位置，依此类推。
程序应该使用嵌套循环，并在外部循环的每次迭代后输出列表，从而输出列表N-1次（其中N是列表的大小），并且该函数不应返回任何值。

到目前为止，我编写的代码确实对列表进行了排序，但无法以应有的方式显示输出。

以下是我尝试过的：
```python
def modified_selection_sort(A:list):
    for i in range(len(A)):
        min_idx = i
        max_idx=i
        for j in range(i+1, len(A)):
            if A[min_idx] > A[j]:
                min_idx = j
            if A[max_idx] < A[j]:
                max_idx = j               
            print(A)    #我尝试在这里打印结果？
        A[max_idx], A[min_idx] = A[min_idx], A[max_idx] #这里是交换部分
             
numbers = [int(number) for number in input().split()]
modified_selection_sort(numbers)

以下是我期望的结果：
假设输入列表是：[30 40 20 10]

[30, 10, 20, 40]
[20, 10, 30, 40]
[10, 20, 30, 40]

但我得到的结果是：

[30, 40, 20, 10]
[30, 40, 20, 10]
[30, 40, 20, 10]
[30, 10, 20, 40]
[30, 10, 20, 40]
[30, 40, 20, 10]

我是否漏掉了某个步骤？我是否应该在j循环内部再添加一个循环，以便输出（n-1）次结果？

<details>
<summary>英文:</summary>

I was trying to write a function called modified_selection_sort that takes a list of int values as a parameter and sorts it increasing order. The function should begin by swapping the largest element into the 
last position first, then the second largest into the second-to-last position, etc. 
The program should use nested loops and output the list after each iteration of the outer loop, 
thus outputting the list N-1 times (where N is the size of the list), and the function should have no return value.

The code that I have written so far does sort the list but I can&#39;t get the output to be displayed in the way it should be.

Here&#39;s what I tried:

def modified_selection_sort(A:list):
for i in range(len(A)):
min_idx = i
max_idx=i
for j in range(i+1, len(A)):
if A[min_idx] > A[j]:
min_idx = j
if A[max_idx] < A[j]:
max_idx = j
print(A) #I tried to print the results here?
A[max_idx], A[min_idx] = A[min_idx], A[max_idx] #here's the swapping

numbers = [int(number) for number in input().split()]
modified_selection_sort(numbers)

Here's what I expected:
say the input list was: [30 40 20 10]

[30, 10, 20, 40]
[20, 10, 30, 40]
[10, 20, 30, 40]

But what I get is:

[30, 40, 20, 10]
[30, 40, 20, 10]
[30, 40, 20, 10]
[30, 10, 20, 40]
[30, 10, 20, 40]
[30, 40, 20, 10]

Am I missing a step somewhere? Should I try making another loop inside the j loop that prints out the output (n-1) number of times?


</details>


# 答案1
**得分**: 2

不需要 `min_idx`。相反，应该从列表的最后一个索引开始，然后反向工作，将未排序部分的项目与`max_idx`处的项目进行比较：

```python
def modified_selection_sort(A):
    for i in range(len(A) - 1, 0, -1):
        max_idx = i
        for j in range(i):
            if A[j] > A[max_idx]:
                max_idx = j
        A[i], A[max_idx] = A[max_idx], A[i]
        print(A)

这样：

modified_selection_sort([30, 40, 20, 10])

输出：

[30, 10, 20, 40]
[20, 10, 30, 40]
[10, 20, 30, 40]

演示：https://replit.com/@blhsing/RequiredCompatibleAnalysts

def modified_selection_sort(A):
    for i in range(len(A) - 1, 0, -1):
        max_idx = i
        for j in range(i):
            if A[j] > A[max_idx]:
                max_idx = j
        A[i], A[max_idx] = A[max_idx], A[i]
        print(A)

modified_selection_sort([30, 40, 20, 10])

[30, 10, 20, 40]
[20, 10, 30, 40]
[10, 20, 30, 40]

答案2

得分: 0

如果您只想在交换后查看列表，请将打印语句直接放在发生交换的那一行下面。

A[max_idx], A[min_idx] = A[min_idx], A[max_idx] # 这里是交换
print(A, min_idx, max_idx)

除此之外，这段代码的逻辑存在问题，它允许在没有益处的情况下交换。打印语句表明程序一直在找到 40 和 10 作为最大值和最小值，然后进行交换，接着再次找到 40 和 10 作为最大值和最小值，然后再次交换，然后以 10 和 20 重复这个过程。

A[max_idx], A[min_idx] = A[min_idx], A[max_idx] #here's the swapping
print(A, min_idx, max_idx)