QuickSort ExampleUse the first number in the list as a ‘pivot’.

13 21 15 9 12 3 14 7 6

First write a list of the numbers smaller than the pivot, in the order in which they appear in the original list.

Divide the list into two sub-lists: those that are smaller than the pivot and those that are larger, as follows:

9 12 3 7 6

9 12 3 7 6

QuickSort ExampleUse the first number in the list as a ‘pivot’.

13 21 15 9 12 3 14 7 6

Next, write down the pivot in its correct position.

Divide the list into two sub-lists: those that are smaller than the pivot and those that are larger, as follows:

9 12 3 7 6

9 12 3 7 6 13

21

QuickSort ExampleUse the first number in the list as a ‘pivot’.

13 21 15 9 12 3 14 7 6

Next, write down the numbers larger than the pivot, in the order in which they appear in the original list.

Divide the list into two sub-lists: those that are smaller than the pivot and those that are larger, as follows:

9 12 3 7 6

9 12 3 7 6 13

21 15

15

14

14

21

QuickSort ExampleThe pivot, 13, is now in its correct position. The next step is to apply the same procedure as before to each of the sub-lists.

13 21 15 9 12 3 14 7 6

Write down the numbers smaller than the pivot, in the order in which they appear in the original sub-list.

Start with the first sub-list, and use the first number in the sub-list as a pivot.

9 12 3 7 6 13 15 143

3

7

7

6

6 13

21

QuickSort Example

13 21 15 9 12 3 14 7 6

Then write down the pivot.

9 12 3 7 6 13 15 143

3

7

7

6

6 9 13

The pivot, 13, is now in its correct position. The next step is to apply the same procedure as before to each of the sub-lists.

Start with the first sub-list, and use the first number in the sub-list as a pivot.

21

QuickSort Example

13 21 15 9 12 3 14 7 6

Then write down the numbers in the sub-list which are greater than the pivot, in the order in which they appear in the original sub-list.

9 12 3 7 6 13 15 143

3

7

7

6

6 9

12

12 13

The pivot, 13, is now in its correct position. The next step is to apply the same procedure as before to each of the sub-lists.

Start with the first sub-list, and use the first number in the sub-list as a pivot.

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

The pivot, 13, is now in its correct position. The next step is to apply the same procedure as before to each of the sub-lists.

Now look at the second sub-list, and use the first number in the sub-list as a pivot.

Write down the numbers smaller than the pivot, in the order in which they appear in the original sub-list.

15

15

14

14

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

The pivot, 13, is now in its correct position. The next step is to apply the same procedure as before to each of the sub-lists.

Now look at the second sub-list, and use the first number in the sub-list as a pivot.

15

15 14

Then write down the pivot.

14

21

In this case there are no numbers greater than the pivot.

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

The numbers 9, 12, 13 and 21 are now in the correct positions. The next step is to apply the same procedure to any sub-lists containing more than one number.

Look at the first sub-list, and use the first number in the sub-list as a pivot.

15 14 21

9 12 13 21

There are no numbers smaller than the pivot, so write down the pivot.

3

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

The numbers 9, 12, 13 and 21 are now in the correct positions. The next step is to apply the same procedure to any sub-lists containing more than one number.

Look at the first sub-list, and use the first number in the sub-list as a pivot.

15 14 21

9 12 13 213

Then write down the numbers in the sub-list which are greater than the pivot, in the order in which they appear in the original sub-list.

7

7 6

6

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

The numbers 9, 12, 13 and 21 are now in the correct positions. The next step is to apply the same procedure to any sub-lists containing more than one number.

15 14 21

9 12 13 213 7 6

Now look at the second sub-list, and use the first number in the sub-list as a pivot.

14

14

Write down the numbers smaller than the pivot, in the order in which they appear in the original sub-list.

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

The numbers 9, 12, 13 and 21 are now in the correct positions. The next step is to apply the same procedure to any sub-lists containing more than one number.

15 14 21

9 12 13 213 7 6

Now look at the second sub-list, and use the first number in the sub-list as a pivot.

14

14

Then write down the pivot.

In this case there are no numbers greater than the pivot.

15

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

There is now just one sub-list containing more than one number.

15 14 21

9 12 13 213 7 6

Use the first number in the sub-list as a pivot.

14 15

9 12 13 213 14 15

Write down the numbers smaller than the pivot, in the order in which they appear in the original sub-list.

6

6

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

There is now just one sub-list containing more than one number.

15 14 21

9 12 13 213 7 6

Use the first number in the sub-list as a pivot.

14 15

9 12 13 213 14 15

Then write down the pivot.

6

6 7

21

QuickSort Example

13 21 15 9 12 3 14 7 6

9 12 3 7 6 13 15 14

3 7 6 9 12 13

There are now no sub-lists containing more than one number, so the list is sorted.

15 14 21

9 12 13 213 7 6 14 15

9 12 13 213 14 156 7

22, 26,14,20,12,9,11,15,10

Quick sort animation

The Simpsons

http://www.youtube.com/watch?v=MtcrEhrt_K0

Lego bubblesort