Sorting Algorithms 2.1 Algorithms Thursday, 26 April 2018 Sorting Algorithms Learning Objective: To be able to demonstrate an understanding of standard sorting algorithms. Success Criteria: I can describe how items are sorted using a
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Sorting Algorithms 2.1 – Algorithms<br>
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Thursday, 26 April 2018 Sorting Algorithms Learning Objective: To be able to demonstrate an understanding of standard sorting algorithms.
Success Criteria:
I can describe how items are sorted using a bubble sort algorithm.
I can write a bubble sort algorithm.
I can describe how items are sorted using an insertion sort algorithm.
I can write an insertion sort algorithm. Unit 2: Computational Thinking, Algorithms & Programming<br>
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Sorting Algorithms You need to know how to complete the following sort algorithms:
Bubble sort
Insertion sort
Merge sort Unit 2: Computational Thinking, Algorithms & Programming<br>
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Bubble Sort A bubble sort works by comparing each item in the list to the item to the right of it. The item is then moved based upon whether it is bigger/smaller. Unit 2: Computational Thinking, Algorithms & Programming 10 2 11 6 5 Step 1: Compare the first two numbers. Are they in order? Adjust them if not. Step 2: 2 10 11 6 5 Move to the next two numbers. Are they in order? Adjust them if not.<br>
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Bubble Sort … Unit 2: Computational Thinking, Algorithms & Programming Step 3: Move to the next two numbers. Are they in order? Adjust them if not. Step 4: 2 6 11 10 5 Move to the next two numbers. Are they in order? Adjust them if not 2 6 11 5 10 Step 5: Once you have been through the entire list, check that they are in order. If they are, great! If not, undertake the same process again until they are in order.<br>
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Bubble Sort: Activity Task: Sort the above using the bubble sort algorithm. Show your steps. Show the order of the list after each adjustment. Unit 2: Computational Thinking, Algorithms & Programming 15 9 22 27 14 44 30 16 51 27 A B Pear Banana Apple Blueberry Pineapple C Rain Lolly Freedom Aeroplane Zebra D<br>
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Insertion Sort Algorithm The insertion sort works by looking at each value in turn and inserting the value into its correct place in the list. Unit 2: Computational Thinking, Algorithms & Programming 9 2 5 8 7 Step 1: Compare the first two items. 9 > 2 so 2 moves position.<br>
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Insertion Sort Algorithm Unit 2: Computational Thinking, Algorithms & Programming 2 5 9 8 7 Step 2: Insert 5 into its correct position. 5 > 2 and 5 < 8 so 5 moves position. Step 3: Insert 8 into its correct position. 8 > 5 and < 9 so 8 moves position. 2 8 5 9 7<br>
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Insertion Sort Algorithm Unit 2: Computational Thinking, Algorithms & Programming Step 4: Insert 7 into its correct position. 7 > 5 and 7 < 8 so 7 moves position. 2 7 5 8 9 2 5 7 8 9 Completed Insertion Sort:<br>
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Insertion Sort: Activity Task: Sort the above using the Insertion sort algorithm. Show your steps. Show the order of the list after each adjustment. Unit 2: Computational Thinking, Algorithms & Programming 4 2 8 9 7 19 5 8 7 15 A B C 40 9 32 27 20<br>
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Merge Sort Algorithm The merge sort algorithm is an example of a divide-and-conquer algorithm and takes advantage of two facts:
Small lists are easier to sort than large lists.
It’s easier to merge two-ordered lists than two unordered lists. Unit 2: Computational Thinking, Algorithms & Programming Split the list in half (the smaller lists are called sub-lists) – the second sub-list should start at the middle item.
Keep repeating step 1 on each sub-list until all the lists only contain one item.
Merge pairs of sub-lists so that each sub-list has twice as many items. Each time you merge sub-lists, sort the items into the right order.
Repeat step 3 until you’ve merged all the sub-lists together.<br>
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Merge Sort: Example Unit 2: Computational Thinking, Algorithms & Programming F P A L T D K H T D K H F P A L K H T D A L F P F P A L T D K H F P A L D T H K A F L P D H K T A D F H K L P T<br>
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Merge Sort Pros & Cons The pros and cons of merge sort algorithms are as follows: Unit 2: Computational Thinking, Algorithms & Programming<br>
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Merge Sort: Activity Task: Sort these items using the merge sort method. Unit 2: Computational Thinking, Algorithms & Programming S A P H J Z E R 19 5 29 1 87 14 61 33 Dog Bird Turtle Horse Snake Goat Lion Bear<br>
