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package Sorts;
/* Java program for Bitonic Sort. Note that this program
works only when size of input is a power of 2. */
public class BitonicSort {
/* The parameter dir indicates the sorting direction,
ASCENDING or DESCENDING; if (a[i] > a[j]) agrees
with the direction, then a[i] and a[j] are
interchanged. */
void compAndSwap(int a[], int i, int j, int dir) {
if ((a[i] > a[j] && dir == 1) || (a[i] < a[j] && dir == 0)) {
// Swapping elements
int temp = a[i];
a[i] = a[j];
a[j] = temp;
}
}
/* It recursively sorts a bitonic sequence in ascending
order, if dir = 1, and in descending order otherwise
(means dir=0). The sequence to be sorted starts at
index position low, the parameter cnt is the number
of elements to be sorted.*/
void bitonicMerge(int a[], int low, int cnt, int dir) {
if (cnt > 1) {
int k = cnt / 2;
for (int i = low; i < low + k; i++) compAndSwap(a, i, i + k, dir);
bitonicMerge(a, low, k, dir);
bitonicMerge(a, low + k, k, dir);
}
}
/* This funcion first produces a bitonic sequence by
recursively sorting its two halves in opposite sorting
orders, and then calls bitonicMerge to make them in
the same order */
void bitonicSort(int a[], int low, int cnt, int dir) {
if (cnt > 1) {
int k = cnt / 2;
// sort in ascending order since dir here is 1
bitonicSort(a, low, k, 1);
// sort in descending order since dir here is 0
bitonicSort(a, low + k, k, 0);
// Will merge wole sequence in ascending order
// since dir=1.
bitonicMerge(a, low, cnt, dir);
}
}
/*Caller of bitonicSort for sorting the entire array
of length N in ASCENDING order */
void sort(int a[], int N, int up) {
bitonicSort(a, 0, N, up);
}
/* A utility function to print array of size n */
static void printArray(int arr[]) {
int n = arr.length;
for (int i = 0; i < n; ++i) System.out.print(arr[i] + " ");
System.out.println();
}
public static void main(String args[]) {
int a[] = {3, 7, 4, 8, 6, 2, 1, 5};
int up = 1;
BitonicSort ob = new BitonicSort();
ob.sort(a, a.length, up);
System.out.println("\nSorted array");
printArray(a);
}
}