Merge pull request #21 from SundaramDubey/patch-3

Adding Bitonic Sort

Algorithms/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; 
+}