We denote with n the number of elements, in our example n = 6. Selection sort is an algorithm where we keep finding the smallest element and then we order them in sequence. (O(n^2) in all three cases.) The list is divided into two partitions: The first list contains sorted items, while the second list contains unsorted items. So no element is swapped. Selection Sort Algorithm with Example is given. Got a tip? Know Thy Complexities! The sorted part is empty at the beginning: We search for the smallest element in the right, unsorted part. Hi Patrik, Your name can also be listed here. If you want to sort the array in descending order, (step 2 in the algorithm) find the largest element rather than the smallest element. Selection sort is easiest to implement and to code than other sorting algorithms. After that, the tests are repeated until the process is aborted. This is all about Selection Sort in C with Explanation. The two elements with the key 2 have thus been swapped to their initial order – the algorithm is unstable. Then we move the border between the array sections one field to the right: We search again in the right, unsorted part for the smallest element. When preparing for technical interviews in the past, I found myself spending hours crawling the internet putting together the best, average, and worst case complexities for search and sorting algorithms so that I wouldn't be stumped when asked about them. Enough theory! I'm a freelance software developer with more than two decades of experience in scalable Java enterprise applications. At every step, you have to find the minimum element and put it in the right place. The two nested loops are an indication that we are dealing with a time complexity* of O(n²). Selection Sort kind of works the other way around: We select the smallest card from the unsorted cards and then – one after the other – append it to the already sorted cards. In computer science, selection sort is an in-place comparison sorting algorithm. You can take the array elements as user input as well. Let’s compare the measurements from my Java implementations. Here are the average values after 100 iterations (a small excerpt; the complete results can be found here): Here as a diagram with logarithmic x-axis: The chart shows very nicely that we have logarithmic growth, i.e., with every doubling of the number of elements, the number of assignments increases only by a constant value. This program and algorithm sort the array in ascending order. Sorting playing cards into the hand is the classic example for Insertion Sort. The time complexity for searching the smallest element is, therefore, O(n²) – also called “quadratic time”. But appearances are deceptive. So the total complexity of the Selection sort algorithm is O(n)* O(n) i.e. Selection Sort’s space complexity is constant since we do not need any additional memory space apart from the loop variables i and j and the auxiliary variables length, minPos, and min. I am working on writing about other sorting algorithms. As a reminder, with Insertion Sort, we have comparisons and shifts averaging up to half of the sorted elements; with Selection Sort, we have to search for the smallest element in all unsorted elements in each step. We go to the next field, where we find an even smaller element in the 2. Then you look for the next larger card and place it to the right of the smallest card, and so on until you finally pick up the largest card to the far right. First, you lay all your cards face-up on the table in front of you. The algorithm can be explained most simply by an example. In total, there are 15 comparisons – regardless of whether the array is initially sorted or not. In the best case, we consider as the array is already sorted. Complexity of Insertion sort. In the second step, the algorithm compares the two rear elements. I keep sharing my coding knowledge and my own experience on. It has an O(n ) time complexity, which makes it inefficient on large lists, and generally performs worse than the similar insertion sort. that the runtime for descending sorted elements is significantly worse than for unsorted elements. No extra space is required (in-place sorting) The drawback of selection sort: It has very high time complexity. You find further information and options to switch off these cookies in our, SelectionSort class in the GitHub repository, overview of all sorting algorithms and their characteristics. So the best case but also the average and worst case complexity of Insertion sort, Insertion. Become a better Java programmer element placed at position ‘ i ’ reaches to the fact that no... 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