Explain the selection sort algorithm.

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Explain the selection sort algorithm.

The selection sort algorithm is a simple comparison-based sorting algorithm. It works by dividing the input list into two parts: the sorted part and the unsorted part. Initially, the sorted part is empty, and the unsorted part contains the entire list.

The algorithm repeatedly selects the smallest (or largest, depending on the sorting order) element from the unsorted part and swaps it with the leftmost element of the unsorted part. This process continues until the unsorted part becomes empty, and the sorted part contains all the elements in the correct order.

Here is a step-by-step explanation of the selection sort algorithm:

1. Find the minimum (or maximum) element in the unsorted part of the list.
2. Swap the found minimum (or maximum) element with the leftmost element of the unsorted part.
3. Move the boundary of the sorted part one element to the right.
4. Repeat steps 1-3 until the unsorted part becomes empty.

Let's consider an example to illustrate the selection sort algorithm. Suppose we have an unsorted list [5, 2, 9, 1, 7].

1. In the first iteration, the minimum element is 1. We swap it with the leftmost element, resulting in [1, 2, 9, 5, 7].
2. The boundary of the sorted part is moved one element to the right, and the unsorted part becomes [2, 9, 5, 7].
3. In the second iteration, the minimum element is 2. We swap it with the leftmost element of the unsorted part, resulting in [1, 2, 9, 5, 7].
4. The boundary of the sorted part is moved one element to the right, and the unsorted part becomes [9, 5, 7].
5. In the third iteration, the minimum element is 5. We swap it with the leftmost element of the unsorted part, resulting in [1, 2, 5, 9, 7].
6. The boundary of the sorted part is moved one element to the right, and the unsorted part becomes [9, 7].
7. In the fourth iteration, the minimum element is 7. We swap it with the leftmost element of the unsorted part, resulting in [1, 2, 5, 7, 9].
8. The boundary of the sorted part is moved one element to the right, and the unsorted part becomes [9].
9. Finally, the last element 9 is already in the correct position, and the algorithm terminates.

The selection sort algorithm has a time complexity of O(n^2), where n is the number of elements in the list. It is not the most efficient sorting algorithm for large lists, but it is simple to understand and implement.