Data Structures & Algorithms

Home , Bubble sort, Cocktail shaker sort, Comparison sort, Insertion sort, Merge sort, Selection sort

DATA STRUCTURES & ALGORITHMS Tutorial 6 Questions

SORTING ALGORITHMS

Required Questions Question 1.

Many operations can be performed faster on sorted than on unsorted data. For which of the following operations is this the case? a. checking whether one word is an anagram of another word, e.g., plum and lump b. findin the minimum value. c. computing an average of values d. finding the middle value (the median) e. finding the value that appears most frequently in the data

Question 2.

In which case, the following sorting algorithm is fastest/slowest and what is the complexity in that case? Explain. a. insertion sort b. selection sort c. bubble sort d. quick sort

Question 3.

Consider the sequence of integers

S = {5, 8, 2, 4, 3, 6, 1, 7}

For each of the following sorting algorithms, indicate the sequence S after executing each step of the algorithm as it sorts this sequence: a. insertion sort b. selection sort c. heap sort d. bubble sort e. merge sort

Question 4. Consider the sequence of integers

T = {1, 9, 2, 6, 4, 8, 0, 7}

Indicate the sequence T after executing each step of the Cocktail sort algorithm (see Appendix) as it sorts this sequence.

Advanced Questions Question 5. A variant of the bubble sorting algorithm is the so-called odd-even transposition sort . Like bubble sort, this algorithm a total of n-1 passes through the array. Each pass consists of two phases: The first phase compares array[i] with array[i+1] and swaps them if necessary for all the odd values of of i. The second phase does the same for the even values of i.

a. Show that the array is guaranteed to be sorted after n-1 passes. b. What is the running time of this algorithm?

Appendix – Cocktail sort Cocktail sort, also known as bidirectional bubble sort, cocktail shaker sort, shaker sort (which can also refer to a variant of selection sort), ripple sort, shuffle sort, shuttle sort or happy hour sort, is a variation of bubble sort that is both a stable sorting algorithm and a comparison sort. The algorithm differs from bubble sort in that it sorts in both directions on each pass through the list. This sorting algorithm is only marginally more difficult to implement than bubble sort, and solves the problem with so-called turtles in bubble sort. (Wikipedia)

Pseudocode procedure cocktailSort( A : list of sortable items ) defined as: do swapped := false for each i in 0 to length( A ) - 2 do: if A[ i ] > A[ i + 1 ] then // test whether the two elements are in the wrong order swap( A[ i ], A[ i + 1 ] ) // let the two elements change places swapped := true end if end for if swapped = false then // we can exit the outer loop here if no swaps occurred. break do-while loop end if swapped := false for each i in length( A ) - 2 to 0 do: if A[ i ] > A[ i + 1 ] then swap( A[ i ], A[ i + 1 ] ) swapped := true end if end for while swapped // if no elements have been swapped, then the list is sorted 2

end procedure

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