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8.Sorting in linear time Hsu, Lih-Hsing. Computer Theory Lab. Chapter 8P.2 8.1 Lower bound for sorting The decision tree model.

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Presentation on theme: "8.Sorting in linear time Hsu, Lih-Hsing. Computer Theory Lab. Chapter 8P.2 8.1 Lower bound for sorting The decision tree model."— Presentation transcript:

1 8.Sorting in linear time Hsu, Lih-Hsing

2 Computer Theory Lab. Chapter 8P.2 8.1 Lower bound for sorting The decision tree model

3 Computer Theory Lab. Chapter 8P.3

4 Computer Theory Lab. Chapter 8P.4 8.2 Counting sort

5 Computer Theory Lab. Chapter 8P.5

6 Computer Theory Lab. Chapter 8P.6 The operation of Counting-sort on an input array A[1..8]

7 Computer Theory Lab. Chapter 8P.7 8.3 Radix sort Used by the card-sorting machines you can now find only in computer museum. RADIX_SORT(A,d) 1 for i  1 to d 2 do use a stable sort to sort array A on digit i

8 Computer Theory Lab. Chapter 8P.8

9 Computer Theory Lab. Chapter 8P.9

10 Computer Theory Lab. Chapter 8P.10 8.4 Bucket sort

11 Computer Theory Lab. Chapter 8P.11 Analysis The running time of bucket sort is taking expectations of both sides and using linearity of expectation, we have

12 Computer Theory Lab. Chapter 8P.12 We claim that We define indicator random variables X ij = I {A[j] falls in bucket i} for i = 0, 1, …, n-1 and j = 1, 2,…,n. thus,

13 Computer Theory Lab. Chapter 8P.13

14 Computer Theory Lab. Chapter 8P.14 Indicator random variable X ij is 1 with probability 1/n and 0 otherwise, and therefore When k  j, the variables X ij and X ik are independent, and hence

15 Computer Theory Lab. Chapter 8P.15 We can conclude that the expected time for bucket sort is  (n)+n·O(2-1/n)=  (n).

16 Computer Theory Lab. Chapter 8P.16


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