Create BitonicSort.cpp

Sorting/BitonicSort.cpp

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+
+/* C++ Program for Bitonic Sort. Note that this program 
+   works only when size of input is a power of 2. */
+   
+#include<stdio.h>
+#include<algorithm.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; 
+}