added mergesort in divide and conquer

Divide and Conquer/MergeSort.cpp

@@ -0,0 +1,64 @@
+#include<iostream>
+using namespace std;
+
+void MergeTwoSortedArrays(int arr[], int start, int end){
+  int* arr1 = new int[end - start + 1];
+  int mid = (start + end)/2;
+  int k = 0;
+  int i1 = start;
+  int i2 = mid + 1;
+
+
+  while(i1 <= mid && i2 <= end)
+  {
+    if(arr[i1] <= arr[i2]){
+      arr1[k++] = arr[i1++];
+    }
+    else{
+      arr1[k++] = arr[i2++];
+    }
+  }
+
+  while(i1 <= mid){
+    arr1[k++] = arr[i1++];
+    }
+
+  while(i2 <= end){
+    arr1[k++]= arr[i2++];
+  }
+
+  for(int i = 0; i < k; i++){
+    arr[start++] = arr1[i];
+  }
+}
+
+void MergeSort(int arr[], int start, int end){
+  if(start>=end)
+  {
+    return;
+  }
+  int  mid = (start +  end)/2;
+
+  MergeSort(arr,start,mid);
+  MergeSort(arr,mid+1,end);
+  MergeTwoSortedArrays(arr,start, end);
+}
+
+int main()
+{
+  int n;
+  cin>>n;
+
+  int arr[100];
+
+  for(int i= 0;i<n ;i++){
+    cin>>arr[i];
+  }
+
+  MergeSort(arr,0,n-1);
+
+  for(int i = 0; i< n;i++){
+    cout<<arr[i]<<endl;
+  }
+
+}