rename Sorting -> sorting (#653)

sorting/BitonicSort.cpp

@@ -0,0 +1,76 @@
+// Source : https://www.geeksforgeeks.org/bitonic-sort/
+
+/* 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;
+}