Select Sort Algorithm in python

Question

I am studying data structures and algorithms and I defined the function [below] to implement the Select Sort Algorithm.... However, the statement for switching minimum values to the beginning of the array doesn't seem to be working. Here is the function definition:

def selectionSort(array: list):
    array_length = len(array)  # this just stores the length of the given list
    _index = 0  # this takes care of dynamically changing the index in which a minimum value is to be found

    for i in array:
        min_value = min(array[_index:array_length])
        if i == min_value:  # if i is the minimum value then do nothing, however update _index
            _index += 1
            continue
        else:  # if i is not the minimum value.... 
            array[_index], array[array.index(min_value)] = min_value, i  # replace i with the minimum number, and move i to the [now previous] position of the minimum number,
            _index += 1  # don'f forget to update _index
    return array

The particular command array[_index], array[array.index(min_value)] = min_value, i doesn't seem to be working and it actually is responsible for switching the position of the minimum value in the array min_value with the currently evaluated value in the array i {if i is not the minimum number min_number}

I have tried testing this function with this array (or list as it is called in python):

[5, 2, 3, 9, 8, 7]

With failed results as the function return the same array that was entered. The reason why I am doing this is that I am trying to see if it is possible to implement a Select Sort algorithm without implementing 2 for loops.

Michael Butscher · Accepted Answer · 2020-10-22 22:25:07Z

2

The line

array[_index], array[array.index(min_value)] = min_value, i

is the same as:

temp = (min_value, i)
array[_index] = temp[0]
array[array.index(min_value)] = temp[1]

First, array[_index] is set to min_value. This means (if not the same minimum value is in a prior index in array) that the following array.index(min_value) returns _index.

Simple solution: Swap expressions:

array[array.index(min_value)], array[_index] = i, min_value

answered Oct 22, 2020 at 22:25

Michael Butscher

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