#nullable enable

​

using System;

using System.Collections.Generic;

using System.Linq;

using System.IO;

using System.Threading.Tasks;

using System.Net.Http;

using System.Text;

​

RecursiveStructure data = new() 

{

    Name = "Parent",

    Children = new RecursiveStructure[]{

        new() 

        {

            Name = "Child 1",

            Children = new RecursiveStructure[]{

                new() 

                {

                    Name = "Grandchild 1",

                    Children = new RecursiveStructure[]{ }

                },

                new() 

                {

                    Name = "Grandchild 2",

                    Children = new RecursiveStructure[]{ }

                },

            }

        },

        new() 

        {

            Name = "Child 2",

            Children = new RecursiveStructure[]{

                new() 

                {

                    Name = "Grandchild 3",

                    Children = new RecursiveStructure[]{ }

                },

                new() 

                {

                    Name = "Grandchild 4",

                    Children = new RecursiveStructure[]{ }

                },

            }

        },

    }

};

​

NormalRecursion(data); // depth-first

Console.WriteLine();

QueueRecursion(data); // width-first

Console.WriteLine();

StackRecursion(data); // depth-first

​

void NormalRecursion(RecursiveStructure data)

{

    // actual recursive logic below

    Console.WriteLine($"NR {data.Name}");

    foreach (var child in data.Children)

        NormalRecursion(child);

}

​

void QueueRecursion(RecursiveStructure data)

{

    var queue = new Queue<RecursiveStructure>();

    queue.Enqueue(data);

    while (queue.Any())

    {

        var current = queue.Dequeue();

        // actual recursive logic below

        Console.WriteLine($"QR {current.Name}");

        foreach (var child in current.Children)

            queue.Enqueue(child);

    }

}

​

void StackRecursion(RecursiveStructure data, int depth = 0)

{

    var stack = new Stack<RecursiveStructure>();

    stack.Push(data);

    while (stack.Any())

    {

        var current = stack.Pop();

        // actual recursive logic below

        Console.WriteLine($"SR {current.Name}");

        foreach (var child in current.Children.Reverse()) // NB we need to reverse child order or they'll be popped backwards

            stack.Push(child);

    }

}

​

​

class RecursiveStructure

{

    public required string Name { get; init; }

    public required IEnumerable<RecursiveStructure> Children { get; init; }  

}

​