Download
1 / 22
220 likes | 231 Views
Sorting. Chapter 4. Sorting. Sorting is one of the most fundamental problem in computer science. It is a useful preprocessing to make short work of other problems. Applications of Sorting. Applications of Sorting. Sorting Algorithms. Selection Sort very little storage; data movement
E N D
Sorting Chapter 4
Sorting • Sorting is one of the most fundamental problem in computer science. • It is a useful preprocessing to make short work of other problems.
Sorting Algorithms • Selection Sort • very little storage; data movement • O(n2) comparidons. • Heapsort • selection sort with right data structure • Insertion Sort • very little storage; optimal comparisons • O(n2) data movement
Sorting agorithms • Quicksort • This algorithm reduces the job of sorting one big array into the job of sorting two smaller arrays by performing a partition step. • The partition separates the array into those elements that are less than the pivot/divider element, and • those which are strictly greater than this pivot/divider element.
Multicriteria Sorting • How can we break ties in sorting using multiple criteria?
Stable Sorting • Identical keys are kept in the same relative order they were in before the sorting. • we could sort by the first name, • then do stable sort by the last name • We know that the final results are sorted by both major and minor keys.
Library Routines • C • stdlib.h contains library functions • qsort • C++ • C++STL • sort • stable_sort • Java • java.util.Arrays • sort(Object[] a) • sort(Object[] a, Comparator c)
Vito’s Family • What is the right version of average to solve Vito’s problem: mean, median, or something else? • mean is easy to compute • median: the middle element in the sorted list. • This can be determined easily after sorting the items. • This element can be determined without sorting the elements using a quicksort like algorithm called quickselect.
