Merge Sort

#include<iostream>
using namespace std;

void merge(int *a,int *b,int *c,int s,int e)
{
    int m=(s+e)/2;
    int i=s;
    int j=m+1;
    int k=s;
    
    while(i<=m and j<=e)
    {
       if(b[i]<=c[j])
       {
          a[k++]=b[i++]; 
       }
       else
       {
           a[k++]=c[j++];
       }
    }
    
    while(i<=m)
    {
        a[k++]=b[i++];
    }
    
    while(j<=e)
    {
        a[k++]=c[j++];
    }
}
void merge_sort(int *a,int s,int e)
{
    //base case
    if(s>=e)
    {
        return;
    }
    //1.divide
    int b[100],c[100];
    int m=(s+e)/2;
    for(int i=s;i<=m;i++)
    {b[i]=a[i];}
    
    for(int i=m+1;i<=e;i++)
    {
        c[i]=a[i];
    }
    //2.sort 
    merge_sort(b,s,m);
    merge_sort(c,m+1,e);
    //3.merge
    merge(a,b,c,s,e);
}
int main()
{
    int a[]={4,1,2,6,0,5};
    int n=sizeof(a)/sizeof(int);
    
    cout<<"before sorting"<<endl;
    for(int i=0;i<n;i++)
    {
        cout<<a[i]<<" ";
    }cout<<endl;
    
    merge_sort(a,0,n-1);
    
    cout<<"after sorting"<<endl;
    for(int i=0;i<n;i++)
    {
        cout<<a[i]<<" ";
    }cout<<endl;
    return 0;
}