merge sort program added

merge_sort.cs

@@ -0,0 +1,102 @@
+#include <iostream>
+using namespace std;
+
+// Merges two subarrays of array[].
+// First subarray is arr[begin..mid]
+// Second subarray is arr[mid+1..end]
+void merge(int array[], int const left, int const mid,
+           int const right)
+{
+    auto const subArrayOne = mid - left + 1;
+    auto const subArrayTwo = right - mid;
+
+    // Create temp arrays
+    auto *leftArray = new int[subArrayOne],
+         *rightArray = new int[subArrayTwo];
+
+    // Copy data to temp arrays leftArray[] and rightArray[]
+    for (auto i = 0; i < subArrayOne; i++)
+        leftArray[i] = array[left + i];
+    for (auto j = 0; j < subArrayTwo; j++)
+        rightArray[j] = array[mid + 1 + j];
+
+    auto indexOfSubArrayOne
+        = 0, // Initial index of first sub-array
+        indexOfSubArrayTwo
+        = 0; // Initial index of second sub-array
+    int indexOfMergedArray
+        = left; // Initial index of merged array
+
+    // Merge the temp arrays back into array[left..right]
+    while (indexOfSubArrayOne < subArrayOne
+           && indexOfSubArrayTwo < subArrayTwo) {
+        if (leftArray[indexOfSubArrayOne]
+            <= rightArray[indexOfSubArrayTwo]) {
+            array[indexOfMergedArray]
+                = leftArray[indexOfSubArrayOne];
+            indexOfSubArrayOne++;
+        }
+        else {
+            array[indexOfMergedArray]
+                = rightArray[indexOfSubArrayTwo];
+            indexOfSubArrayTwo++;
+        }
+        indexOfMergedArray++;
+    }
+    // Copy the remaining elements of
+    // left[], if there are any
+    while (indexOfSubArrayOne < subArrayOne) {
+        array[indexOfMergedArray]
+            = leftArray[indexOfSubArrayOne];
+        indexOfSubArrayOne++;
+        indexOfMergedArray++;
+    }
+    // Copy the remaining elements of
+    // right[], if there are any
+    while (indexOfSubArrayTwo < subArrayTwo) {
+        array[indexOfMergedArray]
+            = rightArray[indexOfSubArrayTwo];
+        indexOfSubArrayTwo++;
+        indexOfMergedArray++;
+    }
+    delete[] leftArray;
+    delete[] rightArray;
+}
+
+// begin is for left index and end is
+// right index of the sub-array
+// of arr to be sorted */
+void mergeSort(int array[], int const begin, int const end)
+{
+    if (begin >= end)
+        return; // Returns recursively
+
+    auto mid = begin + (end - begin) / 2;
+    mergeSort(array, begin, mid);
+    mergeSort(array, mid + 1, end);
+    merge(array, begin, mid, end);
+}
+
+// UTILITY FUNCTIONS
+// Function to print an array
+void printArray(int A[], int size)
+{
+    for (auto i = 0; i < size; i++)
+        cout << A[i] << " ";
+}
+
+// Driver code
+int main()
+{
+    int arr[] = { 12, 11, 13, 5, 6, 7 };
+    auto arr_size = sizeof(arr) / sizeof(arr[0]);
+
+    cout << "Given array is \n";
+    printArray(arr, arr_size);
+
+    mergeSort(arr, 0, arr_size - 1);
+
+    cout << "\nSorted array is \n";
+    printArray(arr, arr_size);
+    return 0;
+}