Data Structure

List #

List is a dynamic size linear data structure. In C#, we use List<T> class.


Add function is used to add a value to the list, and Remove function is used to remove a specific value.

FindAll function can be used to find values that meet certain conditions, and as a language of the MZ generation, it supports lambda expressions.

void debug(List<int> number) {
    Console.WriteLine(string.Join(" ", number));
}

List<int> number = new List<int>() {1, 2, 3};
number.Add(4);
debug(number); // output: 1 2 3 4
debug(number.FindAll(i => i % 2 == 0)); // output: 2 4

number.Remove(3);
debug(number); // output: 1 2 4

Dictionary #

Dictionary is a key-value data structure, In some other languages, it’s called a map, HashMap, or HashTable.


You need to declare a type for the key and the value Dictionary<Key, Value>.

You can put a value in the dictionary by using the Add function.

You can access the value as same way as an array.

Dictionary<string, string> dict = new Dictionary<string, string>();
dict.Add("k1", "hello");
dict.Add("k2", "world");

Console.WriteLine(dict["k1"]); // output: hello

You can add and modify data in the form of dict[key] = value. 

Dictionary<string, string> dict = new Dictionary<string, string>();
dict["k1"] = "hello";
dict["k2"] = "world";
Console.WriteLine(dict["k1"]); // output: hello

dict["k1"] = "halo";
Console.WriteLine(dict["k1"]); // output: halo

An error occurs when you try to access a key that does not exist. 

Dictionary<string, string> phoneNumbers = new Dictionary<string, string>();
phoneNumbers["david"] = "010-XXXX-XXXX";

// Exception occured: The given key 'scalalang' was not present in the dictionary.
try {
    Console.WriteLine($"a phone number of scalalang: {phoneNumbers["scalalang"]}");
} catch (Exception e) {
    Console.WriteLine("Exception occured: {0}", e.Message);
}

Stack #

Stack is a data structure that follows the rule of First-In Last-Out.


The Push(value) function adds a value to the top of a stack, and the Pop() function removes the value at the top of the stack. 

Stack<string> names = new Stack<string>();
names.Push("John");
names.Push("Peter");
names.Push("Mark");
Console.WriteLine(names.Peek()); // output: Mark
names.Pop();
Console.WriteLine(names.Peek()); // output: Peter
Console.WriteLine(names.Count);  // output: 2

Queue #

Queue is a data structure that follows the rule of First-In First-Out.


The queue supports two fundamental operations Enqueue and Dequeue. 

Queue<int> queue = new Queue<int>();
queue.Enqueue(1);
queue.Enqueue(2);
queue.Enqueue(3);
queue.Enqueue(4);

// output: 1 2 3 4
while (queue.Count > 0) 
    Console.WriteLine(queue.Dequeue());

Priority Queue #

Priority Queue is a data structure that the data with higher priority comes out first.


There are two fundamental operations Enqueue and Dequeue.

It’s declared in the form of PriorityQueue<Value, Priority>, where Value is the value and Priority is the priority.

var queue = new PriorityQueue<string, int>();
queue.Enqueue("Task A", 1);
queue.Enqueue("Task B", 4);
queue.Enqueue("Task C", 2);
queue.Enqueue("Task D", 7);
queue.Enqueue("Task E", 3);

while (queue.Count > 0) {
    var task = queue.Dequeue();
    Console.WriteLine($"Task: {task}");
}