FilesExpand file tree

 master

/

IterativeTernarySearch.java

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

74 lines (60 loc) · 2.23 KB

 master

/

IterativeTernarySearch.java

Top

File metadata and controls

• Code
• Blame

74 lines (60 loc) · 2.23 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

package Searches;

import static java.lang.String.format;

import java.util.Arrays;

import java.util.Random;

import java.util.stream.Stream;

/**

* A iterative version of a ternary search algorithm This is better way to implement the ternary

* search, because a recursive version adds some overhead to a stack. But in java the compile can

* transform the recursive version to iterative implicitly, so there are no much differences between

* these two algorithms

*

* <p>Worst-case performance Θ(log3(N)) Best-case performance O(1) Average performance Θ(log3(N))

* Worst-case space complexity O(1)

*

* @author Podshivalov Nikita (https://github.com/nikitap492)

* @see SearchAlgorithm

* @see TernarySearch

* @since 2018-04-13

*/

public class IterativeTernarySearch implements SearchAlgorithm {

@Override

public <T extends Comparable<T>> int find(T[] array, T key) {

int left = 0;

int right = array.length - 1;

while (right > left) {

int leftCmp = array[left].compareTo(key);

int rightCmp = array[right].compareTo(key);

if (leftCmp == 0) return left;

if (rightCmp == 0) return right;

int leftThird = left + (right - left) / 3 + 1;

int rightThird = right - (right - left) / 3 - 1;

if (array[leftThird].compareTo(key) <= 0) {

left = leftThird;

} else {

right = rightThird;

}

}

return -1;

}

public static void main(String[] args) {

// just generate data

Random r = new Random();

int size = 100;

int maxElement = 100000;

Integer[] integers =

Stream.generate(() -> r.nextInt(maxElement)).limit(size).sorted().toArray(Integer[]::new);

// the element that should be found

Integer shouldBeFound = integers[r.nextInt(size - 1)];

IterativeTernarySearch search = new IterativeTernarySearch();

int atIndex = search.find(integers, shouldBeFound);

System.out.println(

format(

"Should be found: %d. Found %d at index %d. An array length %d",

shouldBeFound, integers[atIndex], atIndex, size));

int toCheck = Arrays.binarySearch(integers, shouldBeFound);

System.out.println(

format(

"Found by system method at an index: %d. Is equal: %b", toCheck, toCheck == atIndex));

}

}