Bitonic Sort

Java/Bitonic Sort

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+In Bitonic sequence, elements are first arranged in increasing order, and then after some particular index they start decreasing.
+An array with A[0…i…n-1] is said to be bitonic if there is an index i, such that -
+  A[0] < A[1] < A[2] .... A[i-1] < A[i] > A[i+1] > A[i+2] > A[i+3] > ... >A[n-1]  
+Where, 0 ≤ i ≤ n-1
+
+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;
+        }
+    }
+
+    /* Recursive function to solve the sequence in either ascending or descending order.*/
+    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);
+        }
+    }
+
+    /*Function which produces a bitonic sequence by recursively sorting its two halves in opposite sorting orders. */
+    void bitonicSort(int a[], int low, int cnt, int dir)
+    {
+        if (cnt > 1) {
+            int k = cnt / 2;
+           bitonicSort(a, low, k,1);
+            bitonicSort(a, low + k, k, 0);
+           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();
+    }
+
+    // Driver method
+    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);
+    }
+}