Question

Knowing when to apply a data structure for a given business problem is an important skill for developers to know.

Research the following .NET data structures:

    List
    ArrayList
    LinkedList

Discuss examples of business problems that could be solved using each of the data structures.

Knowing how to sort data in an array and knowing which sorting algorithm to use makes implementing sorting easier.

Discuss different ways to sort an array in C#. What do you see as the advantages and disadvantages of each type of sorting algorithm?

Answer 1

ArrayList, is a dynamic array. What that means is an ArrayList can have any amount of objects and of any type. This data structure was designed to simplify the processes of adding new elements into an array. Under the hood, an ArrayList is an array whose size is doubled every time it runs out of space. Doubling the size of the internal array is a very effective strategy that reduces the amount of element-copying in the long run. We won't get into the proof of that here. The data structure is very simple to use:

ArrayList myArrayList = new ArrayList();
myArrayList.Add(56);
myArrayList.Add("String");
myArrayList.Add(new Form());

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List is the generic version of ArrayList, which means that it behaves exactly the same way, but within a specified type. So for example, a List of integers would work as follows:

List<int> intList = new List<int>();
intList.Add(45);
intList.Add(34);

----------------------------------------------------------------------------------------------LinkedList is a series of objects which instead of having their references indexed (like an Array), stay together by linking to each other, in Nodes.

A LinkedList Node has basically three values: the Object's Value, a reference to the Next node, and a reference to the Previous Node.

What is the point of such C# data structure? Well, adding values to the middle of the list is much faster compared to any other Array type of data structure. It also keeps memory costs down to a minimum. Lists on the other hand use extra space to make future insertions as fast as possible.

LinkedList<int> list = new LinkedList<int>();
list.AddLast(6);

Retrieving a value is not as straight forward:

list.First.Value 
or
list.Last.Value

Since inserting and removing elements is done by updating a couple references, they can be done in constant time. The tradeoff is that accessing elements is no longer a constant time operation. In an array, with a given index an element can be instantly accessed. With a linked list, the references between nodes need to be followed until the desired element is found.

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There are various sorting Algorithms:

• Method 1: Using Array.Sort() and Array.Reverse() Method
  First, sort the array using Array.Sort() method which sorts an array ascending order then, reverse it using Array.Reverse() method.
• Method 2: Using CompareTo() Method
  You can also sort an array in decreasing order by using CompareTo() method.
• Method 3: Using delegate
  Here, first Sort() the delegate using an anonymous method.

• Method 4: Using Iterative way. Sort an array without using any inbuilt function by iterative way.

• Method 5: Using LINQ descending
  LINQ stands for Language Integrated Query. It is a uniform query syntax which is used to retrieve and save the data from the different sources. Here, OrderByDescending sorting method is used for descending order sorting. The LINQ returns IOrderedIEnumerable, which is converted to Array using ToArray() method.