added mergesort cpp in the merge sort folder

merge_sort/merge_sort.cpp

@@ -0,0 +1,84 @@
+#include <iostream>
+using namespace std;
+
+void merge(int arr[], int s, int e, int mid) {
+    int temp[e - s + 1];
+    int i = s;
+    int j = mid + 1;
+    int k = 0;
+
+    // Merge two sorted arrays into a temporary array
+    while (i <= mid && j <= e) {
+        if (arr[i] <= arr[j]) {
+            temp[k] = arr[i];
+            k++;
+            i++;
+        } else {
+            temp[k] = arr[j];
+            k++;
+            j++;
+        }
+    }
+
+    // Copy remaining elements from the first subarray, if any
+    while (i <= mid) {
+        temp[k] = arr[i];
+        k++;
+        i++;
+    }
+
+    // Copy remaining elements from the second subarray, if any
+    while (j <= e) {
+        temp[k] = arr[j];
+        k++;
+        j++;
+    }
+
+    // Copy the merged elements from the temporary array back to the original array
+    for (k = 0, i = s; k < e - s + 1; k++, i++) {
+        arr[i] = temp[k];
+    }
+}
+
+void mergesort(int arr[], int s, int e) {
+    if (s >= e) {
+        return;
+    }
+
+    // Calculate the middle index
+    int mid = s + (e - s) / 2;
+
+    // Recursively sort the first and second halves
+    mergesort(arr, s, mid);
+    mergesort(arr, mid + 1, e);
+
+    // Merge the sorted halves
+    merge(arr, s, e, mid);
+}
+int main() {
+    int n;
+
+    // user input
+    cout << "Enter the size of the array: ";
+    cin >> n;
+    int arr[n];
+    cout << "Enter " << n << " elements: ";
+    for (int i = 0; i < n; i++) {
+        cin >> arr[i];
+    }
+
+    // Call the merge sort function to sort the array
+    mergesort(arr, 0, n - 1);
+
+    // Print the sorted array
+    cout << "Sorted array: ";
+    for (int i = 0; i < n; i++) {
+        cout << arr[i] << " ";
+    }
+
+    return 0;
+}
+
+
+
+