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Task/Sorting-algorithms-Shell-sort/00-TASK.txt

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+{{Sorting Algorithm}}
+[[Category:Sorting]]
+
+;Task:
+Sort an array of elements using the [[wp:Shell sort|Shell sort]] algorithm, a diminishing increment sort. 
+
+The Shell sort   (also known as Shellsort or Shell's method)   is named after its inventor, Donald Shell, who published the algorithm in 1959.
+ 
+Shell sort is a sequence of interleaved insertion sorts based on an increment sequence. 
+The increment size is reduced after each pass until the increment size is 1. 
+
+With an increment size of 1, the sort is a basic insertion sort, but by this time the data is guaranteed to be almost sorted, which is insertion sort's "best case". 
+
+Any sequence will sort the data as long as it ends in 1, but some work better than others. 
+
+Empirical studies have shown a geometric increment sequence with a ratio of about 2.2 work well in practice.
+[http://www.cs.princeton.edu/~rs/shell/]  
+
+Other good sequences are found at the [https://oeis.org/search?q=shell+sort On-Line Encyclopedia of Integer Sequences].
+<br><br>
+