- published: 25 Jan 2016
- views: 4328
In computer science, a selection algorithm is an algorithm for finding the kth smallest number in a list or array; such a number is called the kth order statistic. This includes the cases of finding the minimum, maximum, and median elements. There are O(n) (worst-case linear time) selection algorithms, and sublinear performance is possible for structured data; in the extreme, O(1) for an array of sorted data. Selection is a subproblem of more complex problems like the nearest neighbor and shortest path problems. Many selection algorithms are derived by generalizing a sorting algorithm, and conversely some sorting algorithms can be derived as repeated application of selection.
The simplest case of a selection algorithm is finding the minimum (or maximum) element by iterating through the list, keeping track of the running minimum – the minimum so far – (or maximum) and can be seen as related to the selection sort. Conversely, the hardest case of a selection algorithm is finding the median, and this necessarily takes n/2 storage. In fact, a specialized median-selection algorithm can be used to build a general selection algorithm, as in median of medians. The best-known selection algorithm is quickselect, which is related to quicksort; like quicksort, it has (asymptotically) optimal average performance, but poor worst-case performance, though it can be modified to give optimal worst-case performance as well.
In computer science, selection sort is a sorting algorithm, specifically an in-place comparison sort. It has O(n2) time complexity, making it inefficient on large lists, and generally performs worse than the similar insertion sort. Selection sort is noted for its simplicity, and it has performance advantages over more complicated algorithms in certain situations, particularly where auxiliary memory is limited.
The algorithm divides the input list into two parts: the sublist of items already sorted, which is built up from left to right at the front (left) of the list, and the sublist of items remaining to be sorted that occupy the rest of the list. Initially, the sorted sublist is empty and the unsorted sublist is the entire input list. The algorithm proceeds by finding the smallest (or largest, depending on sorting order) element in the unsorted sublist, exchanging (swapping) it with the leftmost unsorted element (putting it in sorted order), and moving the sublist boundaries one element to the right.
Linear time selection algorithm. The long sequence of values in the middle is the list we're selecting from. I use the space below this to show smaller lists of median values, used for recursively selecting good pivots.
In this video, I show you how the Linear Time Selection algorithm works, although this example of n/3 groups is not actually linear.
Choosing order statistic 11 using randomized selection. The rank pointer is showing which element we want in the sorted list. Once we find out what element does here, we're done even if the rest of the list isn't sorted.
http://xoax.net/ Lesson page: http://xoax.net/comp_sci/crs/algorithms/lessons/Lesson8/ In this algorithms video tutorial, we explain and demonstrate the selection sort algorithm on an array of ints. We also provide C++ code for the selection sort on our lesson page. Please submit all questions to our forum: http://xoax.net/forum/ Copyright 2011 XoaX.net LLC
Learn about the selection sort algorithm and how understanding its programming principles makes coding it easier. Follow along in C++ with Code::Blocks IDE. Curious Video: https://curious.com/humanharddrive/selection-sort-quicksort-algorithm/in/introduction-to-programming-with-c?skip_course=1 Have a comment or suggestion? Contact me via: Email: humanHardDrive@gmail.com Code and Notes: http://full.sc/1lUnZNG Witty T-Shirts: http://humanharddrive.spreadshirt.com/
Watch on Udacity: https://www.udacity.com/course/viewer#!/c-ud262/l-627968607/m-601008602 Check out the full Advanced Operating Systems course for free at: https://www.udacity.com/course/ud262 Georgia Tech online Master's program: https://www.udacity.com/georgia-tech
Linear time selection algorithm. The long sequence of values in the middle is the list we're selecting from. I use the space below this to show smaller lists of median values, used for recursively selecting good pivots.
In this video, I show you how the Linear Time Selection algorithm works, although this example of n/3 groups is not actually linear.
Choosing order statistic 11 using randomized selection. The rank pointer is showing which element we want in the sorted list. Once we find out what element does here, we're done even if the rest of the list isn't sorted.
http://xoax.net/ Lesson page: http://xoax.net/comp_sci/crs/algorithms/lessons/Lesson8/ In this algorithms video tutorial, we explain and demonstrate the selection sort algorithm on an array of ints. We also provide C++ code for the selection sort on our lesson page. Please submit all questions to our forum: http://xoax.net/forum/ Copyright 2011 XoaX.net LLC
Learn about the selection sort algorithm and how understanding its programming principles makes coding it easier. Follow along in C++ with Code::Blocks IDE. Curious Video: https://curious.com/humanharddrive/selection-sort-quicksort-algorithm/in/introduction-to-programming-with-c?skip_course=1 Have a comment or suggestion? Contact me via: Email: humanHardDrive@gmail.com Code and Notes: http://full.sc/1lUnZNG Witty T-Shirts: http://humanharddrive.spreadshirt.com/
Watch on Udacity: https://www.udacity.com/course/viewer#!/c-ud262/l-627968607/m-601008602 Check out the full Advanced Operating Systems course for free at: https://www.udacity.com/course/ud262 Georgia Tech online Master's program: https://www.udacity.com/georgia-tech
How OLSR routing works? How MPR selection algorithm works? Drawbacks of Link State Routing Protocol.
irtual University, Computer Science, CS301, Data Structures, Hashing Animation, Applications of Hashing, When Hashing is Suitable? Sorting, Elementary Selection Algorithms, Selection Sort
In this video tutorial we continue examining the BGP Best Path Selection Algorithm by looking at the 4th criteria: AS_PATH. This BGP Well-Known Mandatory BGP Path Attribute, which is communicated to eBGP peers in UPDATE messages, is used by default in BGP if none of the first three attributes are manipulated. Enjoy!
In this video tutorial I kick off the first of 13 videos that will walk through each and every criteria of the BGP Best Path Selection Algorithm. We start here with the first criteria taking a deep dive look at the Cisco-proprietary WEIGHT parameter. Remember that WEIGHT is NOT a BGP Path Attribute as there is no field in the BGP UPDATE message to communicate the value! Enjoy!
In this video tutorial we continue examining the BGP Best Path Selection Algorithm by looking at the 2nd criteria: LOCAL PREFERENCE. This BGP Well-Known Discretionary BGP Path Attribute, which is communicated to iBGP peers, is used to influence the OUTBOUND flow of traffic from your local Autonomous System (AS). Enjoy!
In this video tutorial we continue examining the Border Gateway Protocol (BGP) Best Path Selection Algorithm by looking at the 3rd criteria: Local Origination. We take a deep dive look at two sets of locally originated Network Layer Reachability Information (NLRI) as we evaluate DEFAULT routing information and NON-DEFAULT routing information. Enjoy!
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