Added Merge sort Algorithm

Sorting/Merge sort/Mergesort.cpp

@@ -0,0 +1,53 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define int long long
+//used for 64 bit integers
+void merge(int a[],int l, int mid,int r){
+    int i=l,j=mid+1,k=0;
+    int c[r-l+1];
+    while(i<=mid && j<=r){
+        if(a[i]<=a[j]){
+            c[k++]=a[i++];
+        }
+        else{
+            c[k++]=a[j++];
+        }
+    }
+    while(i<=mid){
+        c[k++]=a[i++];
+    }
+    while(j<=r){
+        c[k++]=a[j++];
+    }
+    j=l;
+    for(int i=0;i<r-l+1;i++){
+a[j++]=c[i];
+    }
+}
+
+void mergesort(int a[],int l,int r){
+    if(l<r){
+        int mid=l+(r-l)/2;
+        mergesort(a,l,mid);
+        mergesort(a,mid+1,r);
+        merge(a,l,mid,r);
+    }
+}
+
+//main function should always be a 32 bit one so we use int32_t
+int32_t main(){
+       int n;
+   cin >> n;
+   //size of the array
+   int a[n];
+   //declaring an array of size n
+   for (int i = 0; i < n; i++)
+   {
+      cin >> a[i];
+   }
+   mergesort(a,0,n-1);
+   for (int i = 0; i < n; i++)
+   {
+      cout << a[i]<<" ";
+   }
+}