FilesExpand file tree

 master

/

source_code.cpp

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

73 lines (64 loc) · 1.84 KB

 master

/

source_code.cpp

Copy path

Top

File metadata and controls

• Code
• Blame

73 lines (64 loc) · 1.84 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

#include <iostream>

#include <vector>

#include <cstdlib>

using std::vector;

using std::swap;

using std::cout;

using std::endl;

using std::cin;

//this function performs a 3 way partition of the input vector a as follows

//partition A : contains all elements less than the pivot element

//partition B : contains all elements equal to the pivot element

//partition C : contains all elements more than the pivot element

vector<int> partition3(std::vector<int> &a, int l, int r) {

//mid and l start from the the leftmost element

int mid = l;

//_result vector stores the starting and ending position of the repeating pivot element a[l]

vector<int> _result(2);

while(mid <= r) {

if(a[mid] < a[l]) {

swap(a[mid], a[l]);

++l;

++mid;

}else if(a[mid] == a[l]) {

++mid;

}else {

swap(a[r], a[mid]);

--r;

}

}

_result[0] = l;

_result[1] = mid;

return _result;

}

//this function is a recursive implementation of the randomised quick sort algorithm

void randomized_quick_sort(vector<int> &a, int l, int r) {

if (l >= r) {

return;

}

//select a random pivot

int k = l + rand() % (r - l + 1);

//place the pivot in the first index

swap(a[l], a[k]);

//p[0] and p[1] contain the first and last indices of the repeating element in its final position

vector<int> p = partition3(a, l, r);

//recursive call to sort the first half of the remaining array

randomized_quick_sort(a, l, p[0]);

//recursive call to sort second half of the remaining array

randomized_quick_sort(a, p[1], r);

}

int main() {

int n;

std::cin >> n;

vector<int> a(n);

//input n integer elements

for (size_t i = 0; i < a.size(); ++i) {

std::cin >> a[i];

}

//call the randomized_quick_sort function

randomized_quick_sort(a, 0, a.size() - 1);

//display the sorted result

for (size_t i = 0; i < a.size(); ++i) {

std::cout << a[i] << ' ';

}

}