Merge Sort

Merge Sort

@@ -0,0 +1,65 @@
+//it use divide and conquer algorithm
+#include<iostream>
+using namespace std;
+void merge (int arr[],int l, int mid,int r){
+    int n1=mid-l+1;
+    int n2=r-mid;
+    int a[n1];
+    int b[n2]; //we are making two temporary array as we have to compare two values and then inputing the lower value
+    for(int i=0;i<n1;i++){
+        a[i]=arr[l+i];  //as our indexing start with leftmost value of original array
+    }
+    for(int i=0;i<n2;i++){
+        b[i]=arr[mid+1+i];  //as our indexing start with mid+1 value of original array
+    }
+    int i=0;
+    int j=0;
+    int k=l;//our indexinging will start with leftmost value
+    while(i<n1 && j<n2){
+        if(a[i]<b[j]){
+            arr[k]=a[i];
+            k++;
+            i++;
+        }
+        else{
+            arr[k]=b[j];
+            k++;
+            j++;
+        }
+    }
+    while(i<n1){
+        arr[k]=a[i];
+        k++;
+        i++;
+    }
+    while(j<n2){
+        arr[k]=b[j];
+        k++;
+        j++;
+    }
+}
+void mergeSort(int arr[],int l,int r){
+    if(r>l){
+        int mid=(l+r)/2;
+        mergeSort(arr,l,mid);
+        mergeSort(arr,mid+1,r);
+        merge(arr,l,mid,r);
+    }
+}
+int main(){
+int n ;
+cout<<"Enter size of array ";
+cin>>n;
+int arr[n];
+cout<<"Enter values of array "<<endl;
+for(int i=0;i<n;i++){
+    cin>>arr[i];
+}
+mergeSort(arr,0,n);
+for(int i=0;i<n;i++){
+    cout<<arr[i]<<" ";
+}
+return 0;
+}
+
+//check time complexity by your own