冒泡排序

Transcript

1. Bubble Sort
2. Bubble Sort • In bubble sort, the idea of the algorithm is to move higher valued elements generally towards the right and lower value elements generally towards the left. In pseudocode: • Set swap counter to a non-zero value • Repeat until the swap counter is 0: • Reset swap counter to 0 • Look at each adjacent pair • If two adjacent elements are not in order, swap them and add one to the swap counter
3. Bubble Sort 5 2 1 3 6 4 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter Swap Counter -1
4. Bubble Sort 5 2 1 3 6 4 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
5. Bubble Sort 5 2 1 3 6 4 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
6. Bubble Sort 2 5 1 3 6 4 Swap Counter 1 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
7. Bubble Sort 2 5 1 3 6 4 Swap Counter 1 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
8. Bubble Sort 2 1 5 3 6 4 Swap Counter 2 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
9. Bubble Sort 2 1 5 3 6 4 Swap Counter 2 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
10. Bubble Sort 2 1 3 5 6 4 Swap Counter 3 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
11. Bubble Sort 2 1 3 5 6 4 Swap Counter 3 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
12. Bubble Sort 2 1 3 5 6 4 Swap Counter 3 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
13. Bubble Sort 2 1 3 5 4 6 Swap Counter 4 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
14. Bubble Sort 2 1 3 5 4 6 Swap Counter 4 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
15. Bubble Sort 2 1 3 5 4 6 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
16. Bubble Sort 2 1 3 5 4 6 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
17. Bubble Sort 1 2 3 5 4 6 Swap Counter 1 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
18. Bubble Sort 1 2 3 5 4 6 Swap Counter 1 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
19. Bubble Sort 1 2 3 5 4 6 Swap Counter 1 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
20. Bubble Sort 1 2 3 5 4 6 Swap Counter 1 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
21. Bubble Sort 1 2 3 4 5 6 Swap Counter 2 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
22. Bubble Sort 1 2 3 4 5 6 Swap Counter 2 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
23. Bubble Sort 1 2 3 4 5 6 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
24. Bubble Sort 1 2 3 4 5 6 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
25. Bubble Sort 1 2 3 4 5 6 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
26. Bubble Sort 1 2 3 4 5 6 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
27. Bubble Sort 1 2 3 4 5 6 Swap Counter 0 In pseudocode: Set swap counter to a non-zero value Repeat until the swap counter is 0: Reset swap counter to 0 Look at each adjacent pair If two adjacent elements are not in order, swap them and add one to the swap counter
28. Bubble Sort • Worst-case scenario: The array is in reverse order; we have to “bubble” each of the n elements all the way across the array, and since we can only fully bubble one element into position per pass, we must do this n times. • Best-case scenario: The array is already perfectly sorted, and we make no swaps on the first pass.
29. Bubble Sort O(n2) Ω(n)