//  File: mergesort.cpp
//  Merge Sort Routines

#ifndef MERGESORT_CPP
#define MERGESORT_CPP

#include <iostream>
#include <cassert>

using namespace std ;

template <class T>
void merge( T A[], int low1, int high1, int low2, int high2 ) {

   int t=0, i1=low1, i2=low2 ;

   // Sanity check
   assert(low2 == high1 + 1) ;

   // Allocate space for temporary array
   //
   T *temp = new T[high2 - low1 + 1] ;
  
   // while there are elements in both halves, copy the lowest one
   //
   while (i1 <= high1 && i2 <= high2) {
      if (A[i1] < A[i2]) {
         temp[t++] = A[i1++] ;
      } else {
         temp[t++] = A[i2++] ;
      }
   }

   // copy any remaining elements, if any
   //
   while (i1 <= high1) {
	  temp[t++] = A[i1++] ; 
   }
   while (i2 <= high2) {
      temp[t++] = A[i2++] ;
   }

   // copy the now-sorted elements back into the original array 
   //
   for (t = low1; t <= high2; t++) {
      A[t] = temp[t - low1] ;
   }

   delete [] temp ;
}


template <class T>
void MergeSort(T A[], int low, int high) {

//   cout << "MergeSort: low = " << low << ", high = " << high << endl ;

  if (low >= high) return ;
  
   int mid = (low + high)/2 ;
   MergeSort(A, low, mid) ;
   MergeSort(A, mid + 1, high) ;
   
   merge(A, low, mid, mid + 1, high) ;
}

#endif