Selection Sort
Like Bubble Sort, Selection Sort is an early sorting algorithm. Its method is also simple, though somewhat less intuitive.
Selection Sort procedure:
- Select the first element of the array
- Find the smallest element of those to the right and swap the current element with the smallest element
- Repeat steps one and two for each index through the second to last
The algorithm is almost the "opposite" of Bubble Sort, populating the smallest elements first.
Selection Sort always has a time complexity of $O(n^2)$, making it as inefficient as Bubble Sort. However, it has a better use case: low-memory applications.
The space complexity of Selection Sort is constant, $O(1)$. This means that when memory writes are expensive, Selection Sort is a viable choice.
Visualization
I used HTML5 Canvas to render the visualization. Each bar's height represents the magnitude of its value in the array.
The visual shows each step with a small delay so users can see what's really happening, and the bar that is currently moving is highlighted.
The red bar represents the working element, the blue the element that's currently being compared, and the yellow the element the algorithm currently thinks is smallest.
Instructions
The box labeled "Number of elements" determines how many numbers the array to be sorted will contain.
The array will be filled with values from 1 to the number you enter in the box, then shuffled so that it can be resorted.
Enter a value you wish to visualize and click "See it!" to begin the animation.
Use the speed slider to control how fast the animation moves.