Selection Sort

The selection sort is a combination of searching and sorting. During each pass, the unsorted element with the smallest (or largest) value is moved to its proper position in the array.  The number of times the sort passes through the array is one less than the number of items in the array.  In the selection sort, the inner loop finds the next smallest (or largest) value and the outer loop places that value into its proper location. Let's look at our same table of elements using a selection sort for descending order.  Remember, a "pass" is defined as one full trip through the array comparing and if necessary, swapping  elements.

While being an easy sort to program, the selection sort is one of the least efficient.  The algorithm offers no way to end the sort early, even if it begins with an already sorted list. 

// Selection Sort Function for Descending Order
void SelectionSort(apvector <int> &num)
{
      int i, j, first, temp;
      int numLength = num.length( );
      for (i= numLength - 1; i > 0; i--)
     {
           first = 0;                 // initialize to subscript of first element
           for (j=1; j<=i; j++)   // locate smallest between positions 1 and i.
          {
                 if (num[j] < num[first])
                 first = j;
          }
         temp = num[first];   // Swap smallest found with element in position i.
         num[first] = num[i];
         num[i] = temp;
     }
     return;
}