C# Professional - Collections - Exercises

talent-agile

32.7K views

GitHub

Open Source Your Knowledge, Become a Contributor

Technology knowledge has to be shared and made accessible for free. Join the movement.

Create Content

List

Syntax

List<T> obj = new List<T>();

Where "T" generic parameter you can pass any data-type or custom class object to this parameter.

Exercice

// {
        public static List<string> ProcessToKill(List<string> process)
        {
            // Create list of string with initial size to 3.
            List<string> processToKill = new List<string>(3);
            // Show capacity ; here : 3.
            Console.WriteLine(string.Format("Capacity {0}", processToKill.Capacity));
            // Show number of items ; here : 0.
            Console.WriteLine(string.Format("Count {0}", processToKill.Count));
            /// TODO: 
            /// Add items from process to processToKill list 
            /// Process equals "Explorer.exe" don't be added, ignore it
            foreach (var p in processToKill)
            {
                Console.WriteLine(p);
            }           
            return processToKill;
        }
// {

Solution

Replace TODO by this code:

foreach (var p in process) { if (!p.Equals("Explorer.exe")) { processToKill.Add(p); } }

Dictionary

Dictionary is a generic collections which works on key and value pairs. Both key and value pair can have different data-types or same data-types or any custom types (i.e. class objects). Dictionary generic collections is a generic concept applied over Hashtable and it provides fast lookups with keys to get values.

Syntax

Dictionary<T, T> obj = new Dictionary<T, T>();

Where "T" generic parameter you can pass any data-type or custom class object to this parameter.

Exercice

// {
        public class Employee : IEquatable<Employee>
        {
            public int Age;
            public string Name;
            public Employee(string name, int age)
            {
                this.Age = age;
                this.Name = name;
            }
            public bool Equals(Employee other)
            {
                return (this.Age == other.Age && this.Name == other.Name);
            }
        }
        
        public static Dictionary<int, List<string>> GetEmployeesByAge(List<Employee> employees)
        {
            var result = new Dictionary<int, List<string>>();
        
            foreach (var e in employees)
            {
                ///TODO: add employes to result, 
                ///      the key must contain age and 
                ///      values are names list who have the same age.
                
            }
            return result;
        }
// {

Solution

Replace TODO by this code: if(result.ContainsKey(e.Age)) { result[e.Age].Add(e.Name); } else { result.Add(e.Age, new List<string>() { e.Name }); }

LIFO vs FIFO

Stack

A stack is a collection of type Last In First Out ("LIFO").

Syntax

Stack obj = new Stack();

// {
            // Creates and initializes a new Stack.
            Stack<string> myStack = new Stack<string>();
            myStack.Push("Hello");
            myStack.Push("World");
            myStack.Push("!");
            // Displays the properties and values of the Stack.
            Console.WriteLine("\tCount:    {0}", myStack.Count);
            Console.Write("\tValues:");
            foreach (var item in myStack)
            {
                Console.Write("    {0}", item);
            }
// {

Queue

A queue is a collection of type First In First Out ("FIFO").

Syntax

Queue obj = new Queue();

// {
            // Creates and initializes a new Queue.
            Queue<string> myQ = new Queue<string>();
            myQ.Enqueue("Hello");
            myQ.Enqueue("World");
            myQ.Enqueue("!");
            // Displays the properties and values of the Queue.
            Console.WriteLine("\tCount:    {0}", myQ.Count);
            Console.Write("\tValues:");
            foreach(var item in myQ)
            {
                Console.Write("    {0}", item);
            }
// {

Open Source Your Knowledge: become a Contributor and help others learn. Create New Content

Open Source Your Knowledge, Become a Contributor

List

Dictionary

LIFO vs FIFO

Stack

Queue

C# Professional - Basics & OOP - Exercises

C# Professional - LINQ - Exercices

Sales Tax Calculator

C# Tutorial - Part 1: Intro