Sortarea prin interclasare (merge-sort)

Utilizand metoda divide et impera, sa se sorteze prin interclasare un sir

#include<iostream.h>
int a[20],n;

void mergesort(int i,int m,int j)

{int b[20],x=i,k=1,y=m+1; 
while(x<=m && y<=j)
     if (a[x]<a[y])
           b[k++]=a[x++];
     else
           b[k++]=a[y++];
 while (x<=m)
        b[k++]=a[x++];
 while (y<=j)
        b[k++]=a[y++];
 int t=i;       
 for (k=1;k<=(j-i)+1;k++)
        a[t++]=b[k];     
}  

void divimp(int i,int j)
{if (i<j)
    {int m=(i+j)/2;
     divimp(i,m);  
     divimp(m+1,j);
     mergesort(i,m,j);}
}  

void main()
{         
cout<<“n=”;
cin>>n;   
for(int i=1;i<=n;i++)
        {cout<<“a[“<<i<<“]=”;
         cin>>a[i];
        }          
divimp(1,n);
cout<<“vectorul sortat este: “<<endl;
for(i=1;i<=n;i++)
   cout<<a[i]<<‘ ‘;
}