added cpp file

PRACTICE/mergeSort.cpp

@@ -0,0 +1,85 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+void merge(int arr[], int l, int m, int r)
+{
+    int i, j, k;
+    int n1 = m - l + 1;
+    int n2 = r - m;
+
+    // temp left and right sub-arrays
+    int L[n1], R[n2];
+
+    // copy data to temp arrays L[] and R[]
+    for(i = 0; i < n1; i++)
+        L[i] = arr[l + i];
+    for(j = 0; j < n2; j++)
+        R[j] = arr[m + 1 + j];
+
+    // sort and merge the two arrays back
+    i = j = 0;
+    k = l;
+
+    while(i < n1 && j < n2)
+    {
+        if(L[i]<=R[j])
+        {
+            arr[k] = L[i];
+            i++;
+        }
+        else
+        {
+            arr[k] = R[j];
+            j++;
+        }
+        k++;
+    }
+
+    // copy the remaining elements of L[], if there any
+    while(i < n1)
+    {
+        arr[k] = L[i];
+        i++;
+        k++;
+    }
+
+    // copy the remaining elements of R[], if there any
+    while(j < n2)
+    {
+        arr[k] = R[j];
+        j++;
+        k++;
+    }
+}
+
+void mergeSort(int arr[], int l, int r)
+{
+    if(l < r)
+    {
+        int m = l + (r-l)/2;
+        mergeSort(arr, l, m);
+        mergeSort(arr, m+1, r);
+        merge(arr, l, m, r);
+    }
+}
+
+int main()
+{
+    int n;
+    cin>>n;
+    int arr[n];
+    for(int i = 0; i < n; i++) cin>>arr[i];
+
+    cout << "Given array is: " << endl;
+    for(int i = 0; i < n; i++) printf("%d ", arr[i]);
+    printf("\n");
+
+    mergeSort(arr, 0, n-1);
+
+    cout << "Sorted array is: " << endl;
+    for(int i = 0; i < n; i++) printf("%d ", arr[i]);
+    printf("\n");
+
+    return 0;
+}