Develop Reference

Creating A Linked List. C#

I've tried creating linked list/node classes and I'm not sure where to go next. My attempts haven't went well because after creating the classes I'm just not sure what the next step is.
I'm trying to create a program that has a dinosaur node which saves information about the dinosaur such as id, species etc and I want to allow the user to create and remove dinosaurs from the list. So I need to allow the user to input data, I assume there's a way to make dino id get set automatically but I'm not to sure.
I've included the LinkedList.cs and the Node.cs so you can see where I'm going but I have no idea what to do within my program class to utilise the linked list and achieve what I'm trying to do.
Added Program.cs class incase that helps identify/show where I am within the program/what I need to do.
Linked List Class:
using System;
using System.Collections.Generic;
using System.Runtime.ExceptionServices;
using System.Text;
namespace JurrasicFinal
{
public class LinkedList
{
private Node head;
private int count;
public LinkedList()
{
this.head = null;
this.count = 0;
}
public bool Empty
{
get { return this.count == 0; }
}
public int Count
{
get { return this.count; }
}
public object this[int index]
{
get { return this.Get(index); }
}
public object Add(int index, object o)
{
if (index < 0)
throw new ArgumentOutOfRangeException("Index: " + index);
if (index > count)
index = count;
Node current = this.head;
if (this.Empty || index == 0)
{
this.head = new Node(o, this.head);
}
else
{
for (int i = 0; i < index - 1; i++)
{
current = current.Next;
current.Next = new Node(o, current.Next);
}
}
count++;
return o;
}
public object Add(object o)
{
return this.Add(count, o);
}
public object Remove(int index)
{
if (index < 0)
throw new ArgumentOutOfRangeException("Index: " + index);
if (this.Empty)
return null;
if (index >= this.count)
index = count - 1;
Node current = this.head;
object result = null;
if (index == 0)
{
result = current.Data;
this.head = current.Next;
}
else
{
for (int i = 0; index < index - 1; i++) ;
current = current.Next;
result = current.Next.Data;
current.Next = current.Next.Next;
}
count--;
return result;
}
public void Clear()
{
this.head = null;
this.count = 0;
}
public int IndexOf(object o)
{
Node current = this.head;
for (int i = 0; i < this.count; i++)
{
if (current.Data.Equals(o))
return i;
current = current.Next;
}
return -1;
}
public bool Contains(object o)
{
return this.IndexOf(o) >= 0;
}
public object Get(int index)
{
if (index < 0)
throw new ArgumentOutOfRangeException("Index: " + index);
if (this.Empty)
return null;
if (index >= this.count)
index = this.count - 1;
Node current = this.head;
for (int i = 0; i < index; i++)
current = current.Next;
return current.Data;
}
}
}
Node Class:
using System;
using System.Collections.Generic;
using System.Text;
namespace JurrasicFinal
{
public class Node
{
private object data;
private Node next;
private string DinoSpecies;
private string DinoName;
public Node(object data, Node next)
{
this.data = data;
this.next = next;
}
public object Data
{
get { return this.data; }
set { this.data = value; }
}
public Node Next
{
get { return this.next; }
set { this.next = value; }
}
}
}
Program Class:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq.Expressions;
namespace JurrasicFinal
{
class Program
{
class Dinosaur
{
public string Name;
public string Classification;
public char Sex;
}
static void Main(string[] args)
{
LinkedList<Dinosaur> DinoList = new LinkedList<Dinosaur>();
Dinosaur Dino1 = new Dinosaur();
Dino1.Name = "Tyrannosaurus Rex";
Dino1.Classification = "Carnivorous";
Dino1.Sex = 'M';
Dinosaur Dino2 = new Dinosaur();
Dino2.Name = "Velociraptor";
Dino2.Classification = "Carnivorous";
Dino2.Sex = 'F';
Dinosaur Dino3 = new Dinosaur();
Dino3.Name = "Procompsognathus";
Dino3.Classification = "Carnivorous";
Dino3.Sex = 'M';
void printList()
{
Console.WriteLine("Current Queue: ");
Console.WriteLine("\n");
foreach (Dinosaur d in DinoList)
{
Console.WriteLine("Name: " + d.Name);
Console.WriteLine("Classification: " + d.Classification);
Console.WriteLine("Sex " + d.Sex);
Console.WriteLine("\n");
}
Console.WriteLine(Dino1.Name + Dino1.Sex);
}
DinoList.AddLast(Dino1);
DinoList.AddLast(Dino2);
DinoList.AddLast(Dino3);
printList();
Console.WriteLine(DinoList.Count);
FileStream fileStream = File.OpenWrite("E:/Work/Dinosaur.txt");
BinaryWriter writer = new BinaryWriter(fileStream);
foreach (Dinosaur d in DinoList)
{
writer.Write(d.Name);
writer.Write(d.Classification);
writer.Write(d.Sex);
}
writer.Close();
Console.WriteLine("Reading Back From File");
FileStream file = File.OpenRead("E:/Work/Dinosaur.txt");
BinaryReader reader = new BinaryReader(file);
for (int i = 1; i < 3; i++)
{
Dinosaur d = new Dinosaur();
d.Name = reader.ReadString();
d.Classification = reader.ReadString();
d.Sex = reader.ReadChar();
DinoList.AddLast(d);
}
reader.Close();
Console.ReadKey();
}
}
}

I think you might be looking for something like this, which hangs on user input and tries to do simple validation. I made it a bit overly complex to demonstrate some options.
class Sample
{
private static int index = 0;
static void Main(string[] args)
{
LinkedList<Dinosaur> DinoList = new LinkedList<Dinosaur>();
while (true)
{
var dino = new Dinosaur();
dino.Name = GetInput("Enter dino name (q to quit): ");
if (dino.Name == "q" || dino.Name == "Q")
{
break;
}
dino.Classification = GetInput("Enter dino classification: ");
char[] sexes = new char[] {'F', 'f', 'M', 'm'};
while (true)
{
Console.WriteLine("Enter dino sex (M/F): ");
dino.Sex = (char) Console.Read();
if (sexes.Contains(dino.Sex))
{
break;
}
}
int inputIndex = default;
while (true)
{
var indexString = GetInput($"Enter 0-index list position (max {DinoList.Count})");
inputIndex = Convert.ToInt32(indexString);
if (inputIndex <= DinoList.Count)
{
break;
}
}
DinoList.Add(inputIndex, dino);
index++;
Console.WriteLine("Dinosaurs:");
Console.WriteLine(new string('-', 30));
for (var i = 0; i < DinoList.Count; i++)
{
var dinosaur = (Dinosaur) DinoList.Get(i);
Console.WriteLine("Name: " + dinosaur.Name);
Console.WriteLine("Classification: " + dinosaur.Classification);
Console.WriteLine("Sex: " + dinosaur.Sex);
}
}
}
private static string GetInput(string prompt)
{
Console.WriteLine(prompt);
var input = Console.ReadLine();
while (string.IsNullOrWhiteSpace(input))
{
input = Console.ReadLine();
}
return input;
}
}
Note that you have to make your LinkedList and Node into LinkedList<T> and Node<T> but they converted directly, so it's just a bit of typing.
Hope it helps!
Edit: Add classes provided in question, modified to be generic.
public class Node<T>
{
private object data;
private Node<T> next;
private string DinoSpecies;
private string DinoName;
public Node(object data, Node<T> next)
{
this.data = data;
this.next = next;
}
public object Data
{
get { return this.data; }
set { this.data = value; }
}
public Node<T> Next
{
get { return this.next; }
set { this.next = value; }
}
}
public class LinkedList<T>
{
private Node<T> head;
private int count;
public LinkedList()
{
this.head = null;
this.count = 0;
}
public bool Empty
{
get { return this.count == 0; }
}
public int Count
{
get { return this.count; }
}
public object this[int index]
{
get { return this.Get(index); }
}
public object Add(int index, object o)
{
if (index < 0)
throw new ArgumentOutOfRangeException("Index: " + index);
if (index > count)
index = count;
Node<T> current = this.head;
if (this.Empty || index == 0)
{
this.head = new Node<T>(o, this.head);
}
else
{
for (int i = 0; i < index - 1; i++)
{
current = current.Next;
current.Next = new Node<T>(o, current.Next);
}
}
count++;
return o;
}
public object Add(object o)
{
return this.Add(count, o);
}
public object Remove(int index)
{
if (index < 0)
throw new ArgumentOutOfRangeException("Index: " + index);
if (this.Empty)
return null;
if (index >= this.count)
index = count - 1;
Node<T> current = this.head;
object result = null;
if (index == 0)
{
result = current.Data;
this.head = current.Next;
}
else
{
for (int i = 0; index < index - 1; i++) ;
current = current.Next;
result = current.Next.Data;
current.Next = current.Next.Next;
}
count--;
return result;
}
public void Clear()
{
this.head = null;
this.count = 0;
}
public int IndexOf(object o)
{
Node<T> current = this.head;
for (int i = 0; i < this.count; i++)
{
if (current.Data.Equals(o))
return i;
current = current.Next;
}
return -1;
}
public bool Contains(object o)
{
return this.IndexOf(o) >= 0;
}
public object Get(int index)
{
if (index < 0)
throw new ArgumentOutOfRangeException("Index: " + index);
if (this.Empty)
return null;
if (index >= this.count)
index = this.count - 1;
Node<T> current = this.head;
for (int i = 0; i < index; i++)
current = current.Next;
return current.Data;
}
}

getting a performance hit for nested for loop in C#

I have an array of string, a total of(100k). I need to check if the same string has occurred previously, if it occurs all I have to do is return that string. I have written the code using nested for loops, but unfortunately I am getting bad performance. It takes 1.9 mins to process the function correctly for (string[100K]) whereas I am expecting it to finish it within a couple of seconds.
My concern is not the logic. My concern is the LOOP. How to increase the efficiency of the loop.
public string StartMatchingProcess(string[]inputArray)
{
string[] stringArray = inputArray;
string result = string.Empty;
for (long i = 0; i < stringArray.Length; i++)
{
for (long j = 0; j <= i; j++)
{
if(i == j) break;
if (IsPrefix(stringArray[i], stringArray[j]))
{
return stringArray[i];
}
}
}
Console.WriteLine("GOOD SET");
return result;
}
public bool IsPrefix(string string1,string string2)
{
if (AreString1ValuesValid(string1, string2))
{
if (string1 == string2.Substring(0, string1.Length))
{
Console.WriteLine("BAD SET");
Console.WriteLine(string1);
return true;
}
}
else if (AreString2ValuesValid(string1, string2))
{
if (string2 == string1.Substring(0, string2.Length))
{
Console.WriteLine("BAD SET");
Console.WriteLine(string1);
return true;
}
}
return false;
}
public bool AreString1ValuesValid(string string1, string string2)
=> string1.Length <= string2.Length;
public bool AreString2ValuesValid(string string1, string string2)
=> string2.Length <= string1.Length;

Sort the initial array, and you can check neighbors only:
public string StartMatchingProcess(string[] inputArray) {
if (null == inputArray)
throw new ArgumentNullException(nameof(inputArray));
string[] sorted = inputArray.OrderBy(item => item).ToArray();
for (int i = 1; i < sorted.Length; ++i) {
string prior = sorted[i - 1];
string current = sorted[i];
if (current.StartsWith(prior))
return prior;
}
return "";
}
So, you'll have O(n * log(n)) time complexity vs. O(n**2) (initial solution)

It's really bad idea to use nested loops for this task because you have O(n*n) complexity for the answer and need to make 10.000.000.000 calls of Substring() for 100k array.
There is a specific structures for strings. For example, you can use Trie:
public string StartMatchingProcess(string[] inputArray)
{
var trie = new Trie();
foreach(var w in inputArray)
trie.AddWord(w);
foreach(var w in inputArray)
if(trie.HasPrefix(w) || trie.HasWord(w)
return w;
return string.Empty;
}

If you are just trying to determine if your array has duplicate string values, consider LINQ to get the count of the occurences.
string[] arrayTest = new string[] { "hello", "hello", "world"};
string myValue = "hello";
var stringCount = arrayTest.Where(n => n == myValue).Count();
if (stringCount > 1) return myValue;
In the above, we check to see if "hello" is in the array more than once, and if it is, we return it.

Here is a complete solution using linq.
public class Node
{
public char letter { get; }
public int Index { get; set; }
public List<Node> ChildList { get; set; } = new List<Node>();
public Node(char item, int index)
{
Index = index;
letter = item;
}
}
public class NoPrefixSet
{
public Dictionary<char, Node> ParentNode { get; set; } = new Dictionary<char, Node>();
public string GenerateNodes(string[] inputArray)
{
for (int i = 0; i < inputArray.Length; i++)
{
if (IsWordPrefix(inputArray[i]))
{
Console.WriteLine("BAD SET");
Console.WriteLine(inputArray[i]);
return inputArray[i];
}
}
Console.WriteLine("Good Set");
return "Good Set";
}
private void InsertNodeInParent(char item)
=> ParentNode.Add(item, new Node(item, 0));
private bool IsWordPrefix(string word)
{
//Check parent
Node parentNode = null;
bool hasNotInserted = false;
int similarCounter = 0;
if (!ParentNode.Any(a => a.Key == word[0]))
{
InsertNodeInParent(word[0]);
}
parentNode = ParentNode.Where(a => a.Key == word[0]).FirstOrDefault().Value;
for (int letterIndex = 0; letterIndex < word.Length; letterIndex++)
{
if (!parentNode.ChildList.Any(a => a.letter == word[letterIndex]))
{
parentNode.ChildList.Add(new Node(word[letterIndex], letterIndex));
}
else
{
if (!parentNode.ChildList.Where(a => a.letter == word[letterIndex]).First().ChildList.Any() || word.Length == letterIndex+1)
{
if (similarCounter == letterIndex)
return hasNotInserted = true;
}
similarCounter++;
}
parentNode = parentNode.ChildList.Where(a => a.letter == word[letterIndex] && a.Index == letterIndex).First();
}
return hasNotInserted;
}
public void ReadInput()
{
long data = Convert.ToInt64(Console.ReadLine());
string[] stringArray = new string[data];
for (long i = 0; i < data; i++)
{
stringArray[i] = Console.ReadLine();
}
GenerateNodes(stringArray);
}
}

how to to multiply and divide in a static stack?

This is the static array I have been given in making a RPN calculator. From this code the RPN calculator adds and subtracts. Now I need to extend my code to multiply and divide but I cant I don't know how.
public class IntStack
{
private const int maxsize = 10;
private int top = 0;
private int[] array = new int[maxsize];
public void Push(int value)
{
array[top++] = value;
}
public int Pop()
{
return array[--top];
}
public int Peek()
{
return array[top - 1];
}
public bool IsEmpty()
{
return top == 0;
}
public bool IsFull()
{
return top == maxsize;
}
public string Print()
{
StringBuilder output = new StringBuilder();
for (int i = top - 1; i >= 0; i--)
output.Append(array[i] + Environment.NewLine);
return output.ToString();
}
}

Here are some methods you can add to your IntStack class that will perform the multiply and division operations. I've added minimal error checking.
public void Multiply()
{
if (array.Length < 2)
return;
var factor1 = Pop();
var factor2 = Pop();
Push(factor1 * factor2);
}
public void Divide()
{
if (array.Length < 2)
return;
var numerator = Pop();
var divisor = Pop();
if (divisor == 0) { // Return stack back to original state.
Push(divisor);
Push(numerator);
return;
}
Push(numerator / divisor);
}

Checking if singly-linked list is palindrome or not

This is my code.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LinkedList
{
public class Node
{
public int data;
public Node next;
public Node(int data)
{
this.data = data;
next = null;
}
}
public class MyList
{
public Node head;
public MyList()
{
head = null;
}
public void addNode(int data)
{
if(head == null)
{
head = new Node(data);
}
else
{
Node temp = new Node(data);
Node current = head;
while(current.next != null)
{
current = current.next;
}
current.next = temp;
}
}
public void print()
{
if(head == null)
{
Console.WriteLine("List is already empty!");
}
else
{
Node current = head;
while (current != null)
{
Console.Write("|" + current.data + "|-> ");
current = current.next;
}
Console.WriteLine();
}
}
public void addToStart(int data)
{
if(head == null)
{
head = new Node(data);
}
else
{
Node temp = new Node(data);
temp.next = head;
head = temp;
}
}
public void addSorted(int data)
{
if(head == null)
{
head = new Node(data);
}
else if(data < head.data)
{
addToStart(data);
}
else
{
Node current = head.next;
Node previous = head;
Node temp = new Node(data);
while(current != null)
{
if(data < current.data)
{
previous.next = temp;
temp.next = current;
break;
}
previous = current;
current = current.next;
}
}
}
public void removeLast()
{
if(head == null)
{
Console.WriteLine("List is already empty!");
}
else if(head.next == null)
{
head = null;
}
else
{
Node current = head.next;
Node previous = head;
while(current.next != null)
{
previous = current;
current = current.next;
}
previous.next = null;
}
}
public bool isPalindrome()
{
List<int> arr1 = new List<int>();
int i = 0;
Node current = head;
while (current != null)
{
arr1.Add(current.data);
current = current.next;
i++;
}
int[] arr3 = arr1.ToArray();
int count = i;
int[] arr2 = new int[count];
int j = 0;
for (int x = i - 1; x >= 0; x--)
{
arr2[j] = arr3[x];
}
for (int k = 0; k < count; k++)
{
if (arr3[k] != arr2[k])
{
return false;
}
}
return true;
}
}
class Program
{
static void Main(string[] args)
{
MyList a = new MyList();
a.addNode(1);
a.addNode(2);
a.addNode(5);
a.addNode(2);
a.addNode(1);
a.print();
if(a.isPalindrome())
{
Console.WriteLine("Linked List is Palindrome!");
}
else
{
Console.WriteLine("Linked List is Not Palindrome!");
}
}
}
}
My code returns false for the palindrome function every time except when I enter only one value in the linked list.
Also let me know if my method of List<int> is okay or not because I needed it for the palindrome check.

Thankyou for your comments, This is how i solved it.
public bool isPalindrome()
{
int i = 0;
Node current = head;
Node temp = head;
while (temp != null)
{
temp = temp.next;
i++;
}
int[] arr1 = new int[i];
int count = i;
for (int j = 0; j < count; j++)
{
arr1[j] = current.data;
current = current.next;
}
int[] arr2 = new int[count];
int z = 0;
for (int x = i - 1; x >= 0; x--)
{
arr2[z] = arr1[x];
z++;
}
for (int x = 0; x < count; x++)
{
if (arr1[x] != arr2[x])
{
return false;
}
}
return true;
}

Finding minimum value from list

How would i build an algorithm here in the most efficient way possible to find minimum value from list? I know the list hasnt done in the best way but, any ideas how to do ?
I have tried few ways but dont seem to get it work efficiently..
Thanks.
class MainClass
{
public class List
{
public int maxSize = 50;
public int MaxSize
{
get
{
return maxSize;
}
set
{
maxSize = value;
}
}
public int firstEmpty = 0;
public int FirstEmpty
{
get
{
return firstEmpty;
}
set
{
firstEmpty = value;
}
}
public int[] data;
public List()
{
data = new int[maxSize];
}
public int returnValueAtIndex(int i)
{
return data[i];
}
public void setValueAtIndex(int v, int i)
{
data[i] = v;
}
}
public static int FIRST(List L)
{
if (END(L) > 0)
return 0;
else
return -1;
}
public static int END(List L)
{
return L.FirstEmpty;
}
public static int NEXT(int p, List L)
{
if (p >= 0 && p < L.MaxSize && p < END(L))
return p+1;
else
return - 1;
}
public static int PREVIOUS(int p, List L)
{
if (p >= 0 && p < L.MaxSize && p <= END(L))
return p-1;
else
return -1;
}
public static int LOCATE (int x, List L)
{
int i = 0;
while (i<END(L) && RETRIEVE(i, L) != x)
{
i++;
}
if (i != END(L))
return i;
else
return -1;
}
public static int RETRIEVE(int p, List L)
{
if (p >= 0 && p < END(L))
return L.returnValueAtIndex(p);
else
return -1;
}
public static void INSERT(int x, int p, List L)
{
if (p >= 0 && p < L.MaxSize && p <= END(L))
{
if (p == END(L))
{
L.setValueAtIndex(x, p);
}
else
{
for (int i = END(L); i > p; i--)
{
L.setValueAtIndex(L.returnValueAtIndex(i - 1), i);
L.setValueAtIndex(x, p);
}
}
L.FirstEmpty = END(L) + 1;
}
else
Console.WriteLine("Alkiota ei voitu lisätä");
}
public void DELETE(int p, List L)
{
if (p >= 0 && p < END(L))
{
for (int i = p; i < p - 1; i++)
{
L.setValueAtIndex(L.returnValueAtIndex(i + 1), i);
}
L.FirstEmpty = END(L) - 1;
}
}
public void MAKENULL(List L)
{
L.FirstEmpty = 0;
}
public static void PRINT(List L)
{
Console.WriteLine("Listan sisältö:");
for (int i = 0; i < END(L); i++)
{
Console.Write(L.returnValueAtIndex(i) + " ");
}
Console.WriteLine();
}
public static void Main(string[] args)
{
List testilista = new List();
INSERT(2, END(testilista), testilista);
INSERT(7, END(testilista), testilista);
INSERT(9, END(testilista), testilista);
INSERT(12, END(testilista), testilista);
INSERT(9, END(testilista), testilista);
INSERT(38, END(testilista), testilista);
Console.WriteLine("testilista");
PRINT(testilista);
Console.ReadLine();
}
}
}

The easiest way to do that in C# is with LinQ:
var minValue = data.Min();
if you want the highest value:
var maxValue = data.Max();

Note: Answer is not specific to C#
Given an unordered list of numbers, the fastest way to find the smallest number in the list is to look at every element in the list.
var unorderedList = [5,4,3,2,6,7,-23,8,-64,2,0,6];
function findSmallest(anArray){
var lowest = anArray[0];
for(var i = 1; i < anArray.length; i++){
var num = anArray[i];
if(num < lowest){
lowest = num;
}
}
return lowest;
}
var smallest = findSmallest(unorderedList);
console.log(smallest); //prints -64
You can run the code here
hit the run button

I don't think this is the best option. For me there is two ways.
Sort your list by this code.
int valueMin = L.returnValueAtIndex(0);
for (int i = 0; i < END(L); i++)
{
//if the value of i is smaller than the value
if (valueMin < L.returnValueAtIndex(i))
{
//i become the min Value
valueMin = L.returnValueAtIndex(i);
}
}
Console.WriteLine(valueMin);
Console.Read();
Or in C# you can use Array.Sort
Array.Sort(L);
Console.WriteLine(L.returnValueAtIndex(0));
Console.Read();
I hope this will help you !