Merge pull request #102 from Rj-coder-iitian/Rj-coder-iitian

added bitonic sort.

Author: kothariji

Sorting/BitonicSort.cpp

@@ -0,0 +1,72 @@
+/* C++ Program for Bitonic Sort. Note that this program
+	 works only when size of input is a power of 2. */
+#include<bits/stdc++.h>
+using namespace std;
+
+/*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 (dir==(a[i]>a[j]))
+		swap(a[i],a[j]);
+}
+
+/*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 function 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);
+}
+
+// Driver code
+int main()
+{
+	int a[]= {3, 7, 4, 8, 6, 2, 1, 5};
+	int N = sizeof(a)/sizeof(a[0]);
+
+	int up = 1; // means sort in ascending order
+	sort(a, N, up);
+
+	printf("Sorted array: \n");
+	for (int i=0; i<N; i++)
+		printf("%d ", a[i]);
+	return 0;
+}