Sorting

• Sorting is the problem of given an array of items, place those items in order.
  • Given an array and a size, order the array.
• There are many sorting algorithms.
  • We will study selection sort.
    • This is reasonably efficient, but not the best
    • This is simple to understand.
    • It is good to have in your toolbox.
  • Later (CSCI 385) we will study others.
• The big idea
  • Find the smallest element.
  • Move it to the front of the array
  • Repeat this for the rest of the array
• Selection Sort Algorithm

  SelectionSort(A, size);
  
   current = 0
   while current < size do
      small = current
      search = current +1 
      while search < size do
          if A[small] > A[search]
               small = search
          ++search;
      if small != current
          swap(A[small],A[current])
      ++current
  
      

• Performance
  • The nested loops mean that the inside loop will execute n-1, n-2, n-3, ... 2, 1 times.
  • So $T(n) = \Sigma_{i=n-1}^1 i$
  • This is $O(n^2)$