Other structures

• Stacks make a great example of a LIFO structure
• [Non-prioritized] Queues make a great example of a FIFO structure
• In the wilder world, a dictionary only needs support Search, Insert & Delete to be a called a dictionary. We are spoiled by C# :-)

Duh

• In languages where you are doing your own memory management or working with unsorted fixed sized arrays:
  When deleting the n^th item from an array of m elements, it may be more efficent to replace the n^th item with the m^th item, and shrink the end pointer by one.

  Opertaion	Unsorted Array	Sorted Array
  Search	O(n)	O(log n)
  Insert	O(1) [Shove it at the end]	O(n) [Have to find insertion point and remaing elements down one]
  Delete	O(n) --or-- O(1) [If you know where in the array it is and us the trick above]	O(n) [Have to move other populated elements up one]
  Next	O(n) [Preusumes next means 'the item with the next highest key value]	O(1)
  Previous	O(n) [Preusumes next means 'the item with the next lowest key value]	O(1)
  Min key	O(n)	O(1) [First populated element of the array]
  Max key	O(n) --or-- O(1) if you maintain a copy of the maximum key and update it during add and delete operations AND your delete operation is the O(n) version.	O(1) [Last populated element of the array]

• When searching for one string inside another:
  • if we match n characters starting at position i before failing (at position n+i), we can skip ahead and check if the character at position (n+i+i + 1) matches. Knuth-Morris-Pratt takes this a stage further and preprocesses the search string in order to generate a jump table. For example, is the search string contains no letter C before position 8 then following a mismatch we can jump ahead 8 characters and check for C (and only if its correct, check the previous 7 characters)
  • See searching based on a hash value
  • Suffix trees are a good choice if the search text is changing but the searched text does not

• List<Func<int>> actions = new List<Func<int>>();
  for (int i = 0; i < 5; i++)
  {
      actions.Add(() => i * 5);
  }
   
  foreach (Func<int> func in actions) Console.WriteLine(func.Invoke());   // Prints 25 five times

• var results = from c in Categories join p in Products on c.Id equals p.CategoryId select new { CatName = c.Name, CatId = c.Id, ProdName = p.Name };
  foreach (var result in results) Console.WriteLine("{0},{1},{2}", result.CatName, result.CatId, result.ProdName);

• XElement e = new XElement("x", new XElement("y", null));
  Console.WriteLine(e.ToString()); // <x><y /></x>
  

• yield return; (& yeild break;), not return yield.
• .Instersect, .Except, .Union (!= .Concat)

• // First non-repeating character
  var x = (from c in "First non-repeating character".ToUpperInvariant() group c by c into g where g.Count() == 1 select g).FirstOrDefault();
  Console.WriteLine(x.Key);
  

TODO

• INotifyPropertyChanged / BindingList
• Idempotent
• Async
• XML
• Lat / Long