Selection Sort - Python

Selection Sort is a comparison-based sorting algorithm. It sorts an array by repeatedly selecting the smallest (or largest) element from the unsorted portion and swapping it with the first unsorted element. This process continues until the entire array is sorted.

1. First we find the smallest element and swap it with the first element. This way we get the smallest element at its correct position.
2. Then we find the smallest among remaining elements (or second smallest) and swap it with the second element.
3. We keep doing this until we get all elements moved to correct position.

The provided Python code demonstrates the Selection Sort algorithm. Selection Sort has a time complexity of O(n^2). In each iteration, the code finds the minimum element's index in the unsorted portion of the array and swaps it with the current index's element. This gradually sorts the array from left to right. The example initializes an array, applies the selectionSort function to sort it, and then prints the sorted array in ascending order. The sorted array is obtained by repeatedly finding the smallest element in the unsorted portion and placing it in its correct position, resulting in an ordered array: [-202, -97, -9, -2, 0, 11, 45, 88, 747].

def selectionSort(array, size):
   
    for ind in range(size):
        min_index = ind
        for j in range(ind + 1, size):
            # select the minimum element in every iteration
            if array[j] < array[min_index]:
                min_index = j
         # swapping the elements to sort the array
        (array[ind], array[min_index]) = (array[min_index], array[ind])
arr = [-2, 45, 0, 11, -9,88,-97,-202,747]
size = len(arr)
selectionSort(arr, size)
print('The array after sorting in Ascending Order by selection sort is:')
print(arr)

The array after sorting in Ascending Order by selection sort is:
[-202, -97, -9, -2, 0, 11, 45, 88, 747]

Time Complexity:  O(n²).

Auxiliary Space: O(1).

Please refer complete article on Selection Sort for more details!