SOURCE FILE: selectSort.cpp

typedef type-of-array-item dataType;

void SelectionSort(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.
// Calls: IndexOfLargest, Swap.
// ---------------------------------------------------
{
   // Last = index of the last item in the subarray of 
   //        items yet to be sorted,
   // L = index of the largest item found

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

      // select largest item in A[0..Last]
      int L = IndexOfLargest(A, Last+1);

      // swap largest item A[L] with A[Last]
      Swap(A[L], A[Last]);
   }  // end for
}  // end SelectionSort

int IndexOfLargest(const dataType A[], int Size)
// ---------------------------------------------------
// Finds the largest item in an array.
// Precondition: A is an array of Size items, 
// Size >= 1.
// Postcondition: Returns the index of the largest 
// item in the array. The arguments are unchanged.
// ---------------------------------------------------
{
   int IndexSoFar = 0;  // index of largest item 
                        // found so far

   for (int CurrentIndex = 1; CurrentIndex < Size; 
                              ++CurrentIndex)
   {  // Invariant: A[IndexSoFar] >= 
      //            A[0..CurrentIndex-1]
      if (A[CurrentIndex] > A[IndexSoFar])
         IndexSoFar = CurrentIndex;
   }  // end for

   return IndexSoFar;  // index of largest item
}  // end IndexOfLargest

void Swap(dataType& X, dataType& Y)
// ---------------------------------------------------
// Swaps two items.
// Precondition: X and Y are the items to be swapped.
// Postcondition: Contents of actual locations that X 
// and Y represent are swapped.
// ---------------------------------------------------
{
   dataType Temp = X;
   X = Y;
   Y = Temp;
}  // end Swap