Question

Add a CountGroups method to the linked list class below (OurList). It returns the number of groups of a value from the list. The value is passed into the method. A group is one or more values.

Examples using strings:
A list contains the following strings: one, one, dog, dog, one, one, one, dog, dog, dog, dog, one, one, dog, one
   CountGroup(“one”) prints 4 groups of one's
   CountGroup(“dog”) prints 3 groups of dog's

Do not turn in the code below. Turn in only your method.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace LinkListExample
{
    public class OurList<T>
    {
        private class Node
        {
            public T Data { get; set; }
            public Node Next { get; set; }
            public Node(T paramData = default(T), Node paramNext = null)
            {
                this.Data = paramData;
                this.Next = paramNext;
            }
        }

        private Node first;

        public OurList()
        {
            first = null;
        }

        public void Clear()     // shown in class notes
        {
            first = null;
        }

        public void AddFirst(T data)     // shown in class notes
        {
            this.first = new Node(data, this.first);
        }

        public void RemoveFirst()     // shown in class notes
        {
            if (first != null)
                first = first.Next;
        }

        public void AddLast(T data)     // shown in class notes
        {
            if (first == null)
                AddFirst(data);
            else
            {
                Node pTmp = first;
                while (pTmp.Next != null)
                    pTmp = pTmp.Next;

                pTmp.Next = new Node(data, null);
            }
        }

        public void RemoveLast()     // shown in class notes
        {
            if (first == null)
                return;
            else if (first.Next == null)
                RemoveFirst();
            else
            {
                Node pTmp = first;
                while (pTmp.Next != null && pTmp.Next.Next != null)
                    pTmp = pTmp.Next;

                pTmp.Next = null;
            }
        }

        public void Display()     // shown in class notes
        {
            Node pTmp = first;
            while (pTmp != null)
            {
                Console.Write("{0}, ", pTmp.Data);
                pTmp = pTmp.Next;
            }
            Console.WriteLine();
        }

        public bool IsEmpty()     // shown in class notes
        {
            if (first == null)
                return true;
            else
                return false;
        }
     }
}

Answer 1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

    class OurList<T>
    {
        private class Node
        {
            public T Data { get; set; }
            public Node Next { get; set; }
            public Node(T paramData = default(T), Node paramNext = null)
            {
                this.Data = paramData;
                this.Next = paramNext;
            }
        }

        private Node first;

        public OurList()
        {
            first = null;
        }

        public void Clear()     // shown in class notes
        {
            first = null;
        }

        public void AddFirst(T data)     // shown in class notes
        {
            this.first = new Node(data, this.first);
        }

        public void RemoveFirst()     // shown in class notes
        {
            if (first != null)
                first = first.Next;
        }

        public void AddLast(T data)     // shown in class notes
        {
            if (first == null)
                AddFirst(data);
            else
            {
                Node pTmp = first;
                while (pTmp.Next != null)
                    pTmp = pTmp.Next;

                pTmp.Next = new Node(data, null);
            }
        }

        public void RemoveLast()     // shown in class notes
        {
            if (first == null)
                return;
            else if (first.Next == null)
                RemoveFirst();
            else
            {
                Node pTmp = first;
                while (pTmp.Next != null && pTmp.Next.Next != null)
                    pTmp = pTmp.Next;

                pTmp.Next = null;
            }
        }

        public void Display()     // shown in class notes
        {
            Node pTmp = first;
            while (pTmp != null)
            {
                Console.Write("{0}, ", pTmp.Data);
                pTmp = pTmp.Next;
            }
            Console.WriteLine();
        }

        public bool IsEmpty()     // shown in class notes
        {
            if (first == null)
                return true;
            else
                return false;
        }

    
    public int CountGroups(T search) {
        if(first == null) {
            return 0;
        }
        Node tmp = first;
        
        int count = 0;
        T last = default(T);
        while(tmp != null) {
            if(tmp.Data.Equals(search)) {
                // if this was same as what we got previously, then do 
                // not increment group count.
                if(!tmp.Data.Equals(last)) {
                    count++;
                }
            }
            last = tmp.Data;
            tmp = tmp.Next;
        }
        return count;
    }
     }


class MainClass {
  public static void Main (string[] args) {
    OurList<String> l = new OurList<String>();

    l.AddLast("one");
    l.AddLast("one");
    l.AddLast("dog");
    l.AddLast("dog");
    l.AddLast("one");
    l.AddLast("one");
    l.AddLast("one");
    l.AddLast("dog");
    l.AddLast("dog");
    l.AddLast("dog");
    l.AddLast("dog");
    l.AddLast("one");
    l.AddLast("one");
    l.AddLast("dog");
    l.AddLast("one");

    Console.WriteLine (l.CountGroups("one"));
    Console.WriteLine (l.CountGroups("dog"));
  }
}

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