Add recursive Merge Sort

recursion/MergeSort.cs

@@ -0,0 +1,36 @@
+namespace Merge_Sort
+{
+    public class MergeSort
+    {
+        public static void SortBy(int[] array, int leftBorder, int rightBorder)
+        {
+            if (leftBorder >= rightBorder)
+                return;
+            int middle = (leftBorder + rightBorder) / 2;
+            SortBy(array, leftBorder, middle);
+            SortBy(array, middle+1, rightBorder);
+
+            int[] buf = new int[rightBorder-leftBorder+1];
+
+            int i = leftBorder;         //index of left array
+            int j = middle + 1;         //index of right array
+            int k = 0;                  //index of final array
+            while (i <= middle && j <= rightBorder)
+            {
+                if (array[i] < array[j])
+                    buf[k++] = array[i++];
+                else
+                    buf[k++] = array[j++];
+            }
+            //Add the tail of right array
+            while (j <= rightBorder)   
+                buf[k++] = array[j++];
+            //Add the tail of left array
+            while (i <= middle)  
+                buf[k++] = array[i++];
+
+            for (k = 0; k < rightBorder - leftBorder + 1; k++)
+                array[leftBorder + k] = buf[k];
+        }
+    }
+}