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The Basics of the Selection Sort Algorithm
What is Selection Sort?
Selection sort is a simple and intuitive sorting algorithm that operates by dividing the input into two separate parts: the sorted and unsorted portions. It repeatedly selects the smallest (or largest) element from the unsorted part and places it in its correct position within the sorted part. This process is continued until the entire list is sorted.
How does Selection Sort work?
The algorithm starts by assuming the entire list is unsorted. It then scans the list to find the minimum element and swaps it with the first unsorted element. This effectively expands the sorted portion and shrinks the unsorted portion by one element. The process is repeated with the remaining unsorted portion until the entire list is sorted.
Here is a step-by-step breakdown of the selection sort algorithm:
1. Find the minimum element in the unsorted portion of the list.
2. Swap this minimum element with the first unsorted element.
3. Expand the sorted portion by one element and reduce the unsorted portion by one element.
4. Repeat steps 1-3 until the entire list is sorted.
Example:
Let’s illustrate the selection sort algorithm with an example. Consider the following unsorted list of integers: [7, 4, 1, 9, 2].
First pass: Step 1 selects 1 as the minimum element. It is swapped with 7, resulting in [1, 4, 7, 9, 2].
Second pass: Step 1 selects 2 as the minimum element. It is swapped with 4, resulting in [1, 2, 7, 9, 4].
Third pass: Step 1 selects 4 as the minimum element. Since it is already in its correct position, there is no need to swap.
Fourth pass: Step 1 selects 7 as the minimum element. Again, it is in its correct position.
The algorithm terminates and the final sorted list is [1, 2, 4, 7, 9].
Time Complexity and Performance
Selection sort has a time complexity of O(n^2). This means that its performance is not suitable for large datasets. However, it does have the advantage of having a small and straightforward implementation.
Overall, selection sort is an elementary sorting algorithm that is mainly used for educational purposes or for sorting small datasets. It may not be the most efficient algorithm in terms of performance, but it helps in understanding the basic principles of sorting.
Note: When dealing with large datasets, it is recommended to use more efficient sorting algorithms such as merge sort or quicksort.
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