Selection Sort

Successively find the nth smallest value and swap it with the current nth value.

Analysis

Objects	Type	Kind	Movement	Name
array to be sorted	int[ ]	varying	received & passed back	arr
# of elements in array	int	varying	received	n
index of smallest element	int	varying	local	smallIndex
temporary for swapping	int	varying	local	temp
index counters	int, int	varying	local	pass, j

Algorithm

1. For pass from 0 to n-2 by 1 do (scan the sublist starting at index pass)

   1.1

   Set smallIndex to pass (current index of smallest)

   1.2

   For j from pass+1 to n-1 by 1 do

   1.2.1 If arr[j] < arr[smallIndex] then (found smaller)

   1.2.1.1 Set smallIndex to j

   1.3

   If smallIndex not equal pass (exchange elements if needed)

   1.3.1 Set temp to arr[pass]

   1.3.2 Set arr[pass] to arr[smallIndex]

   1.3.3 Set arr[smallIndex] to temp

Code

void SelectionSort (int arr[], int n)
{
   for (int pass = 0; pass < n-1; pass++)
   {
      // index of the smallest value in sublist
      int smallIndex = pass;  

      // scan the sublist starting at pass+1
      for (int j = pass+1; j < n; j++)  
         if (arr[j] < arr[smallIndex])  // found smaller
            smallIndex = j;

      // swap values, if needed
      if (smallIndex != pass)
      {
         int temp = arr[pass];
         arr[pass] = arr[smallIndex];
         arr[smallIndex] = temp;
      }  // end swap
   }  // end for
}  // end SelectionSort