Sorting an Array: The Quick Sort

1
Sorting an ArrayThe Quick Sort

• Lecture 32 Mon, Nov 25, 2002

2
The Quick Sort

• The Quick sort algorithm is considerably more
  complicated than those of the bubble sort,
  selection sort, or insertion sort.
• Efficiency
• Average case requires O(n log n) comparisons.
• Best case requires O(n) comparisons.
• Worst case requires O(n2) comparisons.
• The worst case is exceedingly unlikely.

3
The Quick Sort

• Facts about the Quick sort.
• The algorithm is recursive, as are most of the
  complex sorting algorithms.
• It is, on average, the fastest known sorting
  algorithm.
• It is the most commonly used sorting algorithm.
• It is the most analyzed sorting algorithm.
• There is a library function qsort() in cstdlib.

4
Examples of a Quick Sort

• QuickSort.cpp
• QuickSortTimer.cpp
• date.cpp
• rational.cpp
• point.cpp