3.4 selection sort
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Selection Sort
Transcript of 3.4 selection sort
Selection Sort
Selection Sort: Idea
1. We have two group of items: sorted group, and unsorted group
2. Initially, all items are in the unsorted group. The sorted group is empty. We assume that items in the unsorted
group unsorted. We have to keep items in the sorted group
sorted.
Selection Sort: Cont’d
1. Select the “best” (eg. smallest) item from the unsorted group, then put the “best” item at the end of the sorted group.
2. Repeat the process until the unsorted group becomes empty.
Selection Sort Example
35 65 30 60 20 scan 0-4, smallest 20
swap 35 and 2020 65 30 60 35 scan 1-4,
smallest 30swap 65 and 30
20 30 65 60 35 scan 2-4, smallest 35
swap 65 and 3520 30 35 60 65 scan 3-4,
smallest 60swap 60 and 60
20 30 35 60 65 done
Chapter 10: Sorting
4
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 6 2
Comparison
Data Movement
Sorted
Largest
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Selection Sort
5 1 3 4 2 6
Comparison
Data Movement
Sorted
Largest
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Largest
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Largest
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
2 1 3 4 5 6
Comparison
Data Movement
Sorted
Largest
Selection Sort
1 2 3 4 5 6
Comparison
Data Movement
Sorted
Selection Sort
1 2 3 4 5 6
Comparison
Data Movement
Sorted
DONE!
4240 2 1 3 3 4 0 -1 655843
40 2 1 43 3 4 0 -1 42 65583
40 2 1 43 3 4 0 -1 58 3 6542
40 2 1 43 3 65 0 -1 58 3 42 4
Selection Sort: Example
4240 2 1 3 3 4 0 655843-1
42-1 2 1 3 3 4 0 65584340
42-1 2 1 3 3 4 655843400
42-1 2 1 0 3 4 655843403
Selection Sort: Example
1
42-1 2 1 3 4 6558434030
42-1 0 3 4 6558434032
1 42-1 0 3 4 6558434032
1 420 3 4 6558434032-1
1 420 3 4 6558434032-1
Selection Sort: Example
Selection Sort: Analysis
Running time: Worst case: O(N2) Best case: O(N2)
