Data Structures using C++

   #include <iostream.h> 
    int a[50]; 
    void merge(int,int,int); 
    void merge_sort(int low,int high) 
    { 
      int mid; 
      if(low<high) 
      { 
        mid=(low+high)/2; 
        merge_sort(low,mid); 
        merge_sort(mid+1,high); 
        merge(low,mid,high); 
      } 
    } 
    void merge(int low,int mid,int high) 
    { 
      int h,i,j,b[50],k; 
      h=low; 
      i=low; 
      j=mid+1; 
      while((h<=mid)&&(j<=high)) 
      { 
        if(a[h]<=a[j]) 
        { 
          b[i]=a[h]; 
          h++; 
        } 
        else 
        { 
          b[i]=a[j]; 
          j++; 
        } 
        i++; 
      } 
      if(h>mid) 
      { 
        for(k=j;k<=high;k++) 
        { 
          b[i]=a[k]; 
          i++; 
        } 
      } 
      else 
      { 
        for(k=h;k<=mid;k++) 
        { 
          b[i]=a[k]; 
          i++; 
        } 
      } 
      for(k=low;k<=high;k++) 
      a[k]=b[k]; 
    } 
    void main() 
    { 
      int num,i; 
      cout<<"MERGE SORT PROGRAM"<<endl; 
      cout<<"Please Enter THE NUMBER OF ELEMENTS you want to sort [THEN 
      PRESS ENTER]:"<<endl; 
      cin>>num; 
      cout<<endl; 
      cout<<"Now, Please Enter the ( "<< num <<" ) numbers (ELEMENTS) [THEN 
      PRESS ENTER]:"<<endl; 
      for(i=1;i<=num;i++) 
      { 
        cin>>a[i] ; 
      } 
      merge_sort(1,num); 
      cout<<endl; 
      cout<<"So, the sorted list (using MERGE SORT) will be :"<<endl; 
      cout<<endl<<endl; 
      for(i=1;i<<=num;i++) 
      cout<<a[i]<<" "; 
      cout<<endl<<endl<<endl<<endl; 
    }