SOURCE FILE: insertSort.cpp

void InsertionSort(dataType A[], int N)
// ---------------------------------------------------
// Sorts the items in an array into ascending order.
// Precondition: A is an array of N items.
// Postcondition: The array A is sorted into ascending
// order; N is unchanged.
// ---------------------------------------------------
{
   // Unsorted = first index of the unsorted region, 
   // Loc = index of insertion in the sorted region, 
   // NextItem = next item in the unsorted region

   // initially, sorted region is A[0], 
   //            unsorted region is A[1..N-1];
   // in general, sorted region is A[0..Unsorted-1], 
   //             unsorted region is A[Unsorted..N-1]

   for (int Unsorted = 1; Unsorted < N; ++Unsorted)
   {  // Invariant: A[0..Unsorted-1] is sorted

      // find the right position (Loc) in 
      // A[0..Unsorted] for A[Unsorted], which is the 
      // first item in the unsorted region; 
      // shift, if necessary, to make room
      dataType NextItem = A[Unsorted];
      int Loc = Unsorted;

      for (;(Loc > 0) && (A[Loc-1] > NextItem); --Loc)
         // shift A[Loc-1] to the right
         A[Loc] = A[Loc-1];
      // Assertion: A[Loc] is where NextItem belongs

      // insert NextItem into Sorted region
      A[Loc] = NextItem;
   }  // end for
}  // end InsertionSort