Zabin Visram Room CS115 Lecture Structure

References

Exchange Sort (bubble Sort)

CS126 ZV 2005 Exchange Sort(Bubble Sort)

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Exchange sort

 Basic operation of Exchange sort is the exchange of adjacent pair of elements  Overall sort consist of a number of passes over the data  Each pass starts at one end of the array and works toward the other end  Each pair of elements that are out of order are exchanged CS126 ZV 2005 Exchange Sort(Bubble Sort)

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Exchange Sort

390 250 182 45 235 250 390 182 45 235 250 182 390 45 235 250 182 45 390 235 250 182 45 235

390 (a) (b) (c ) (d) (e)

The first pass of an exchange sort CS126 ZV 2005 Exchange Sort(Bubble Sort) (a) In first pass 390 is compared with 205; then exchanged as 250 is smaller (b) 390 is compared with 182, they exchanged. Result shown in (c ) In (c )390 is compared with 45, they exchanged Then in (d) 390 is compared with 235 and exchanged Result is (e) – regarding the columns as arrays - element 390 has ‘bubbled’ from index 0 to highest index (4)

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bubbling

 The elements with largest value are moving slowly or

bubbling

to the top  If no exchanges are made during one pass over the data, the data have been sorted and process terminates CS126 ZV 2005 Exchange Sort(Bubble Sort)

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Analysis

 The first pass moves the largest element to the

n

th, forming a sorted list of one.

 The second pass has to consider only

n

-1 elements  The second pass moves the second largest element to the n-1 position.  Therefore the third pass only needs to consider

n

-2 elements and so on CS126 ZV 2005 Exchange Sort(Bubble Sort)

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public static void bubbleSort(int data[], int n) { //pre: 0 <= n <= data.length

//post: values in data[0..n-1] are in //ascending order int numSorted = 0; //number of values //in order while (numSorted < n) { //bubble a large element to correct //position for (int index = 1; index

CS126 ZV 2005 Exchange Sort(Bubble Sort)

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public static void bubbleSort(int data[], int n) { //pre: 0 <= n <= data.length

//post: values in data[0..n-1] are in //ascending order int numSorted = 0; //number of values //in order while (numSorted < n) { //bubble a large element to correct //position for (int index = 1; index

//post: data[i] and data[j] are exchanged int temp; temp = data[i]; 7

Disadvantages

  Two disadvantages of this sort are: (i) the use of swap (requiring three assignments) within the inner loop; (ii) the fact that moves are never by more than one position at a time. (Compare selection sort which has no moves in the inner loop and elements may move large distances.) CS126 ZV 2005 Exchange Sort(Bubble Sort)

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Demonstration of Bubble Sort

 http://www.cosc.canterbury.ac.nz/people/m ukundan/dsal/BSort.html

CS126 ZV 2005 Exchange Sort(Bubble Sort)

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