Homework "generic list"

1. (6 points) Build a simple class that implements a generic list. Basically only one method, push, is needed. Something like

   public class genlist<T>{
   	public T[] data;
   	public int size => data.Length; // property
   	public T this[int i] => data[i]; // indexer
   	public genlist(){ data = new T[0]; }
   	public void add(T item){ /* add item to the list */
   		T[] newdata = new T[size+1];
   		for(int i=0;i<size;i++)newdata[i]=data[i];
   		newdata[size]=item;
   		data=newdata;
   	}
   }
   

   Suppose you have an input file with a table of numbers separated by blanks and/or tabs, like this

   129.24 24.8             4.847
   		88.6   33.745 7.78
   30.39  99.811              6.723
       -1.33   96.3   2.23
   

   Create a Main function that reads such a table from the standard input into a genlist<double[]> and the prints the table into standard output in exponential format. Something like

   var list = new genlist<double[]>
   char[] delimiters = {' ','\t'};
   var options = StringSplitOptions.RemoveEmptyEntries;
   for(string line = ReadLine(); line!=null; line = ReadLine()){
   	var words = line.Split(delimiters,options);
   	int n = words.Length;
   	var numbers = new double[n];
   	for(int i=0;i<n;i++) numbers[i] = double.Parse(words[i]);
   	list.push(numbers);
          	}
   for(int i=0;i<list.size;i++){
   	var numbers = list.data[i];
   	foreach(var number in numbers)Write($"{number:e} ");
   	WriteLine();
           }
   

2. (3 points) Improve the speed of the "push" method by increasing the capacity of the data-array not by one element, but instead by doubling it. That should decrease the amount of array copying significantly for the price of increased memory usage. Something like

   public class genlist<T>{
   	public T[] data;
   	public int size=0,capacity=8;
   	public genlist(){ data = new T[capacity]; }
   	public void push(T item){ /* add item to list */
   		if(size==capacity){
   			T[] newdata = new T[capacity*=2];
   			for(int i=0;i<size;i++)newdata[i]=data[i];
   			data=newdata;
   			}
   		data[size]=item;
   		size++;
   	}
   }
   

   Implement void remove(int i) method that removes element number "i".

3. (1 point) Implement generic list using a chain of nodes,

   public class node<T>{
   	public T item;
   	public node<T> next;
   	public node(T item){this.item=item;}
   }
   

   Something like this,

   public class list<T>
           public node<T> first=null,current=null;
           public void push(T item){
                   if(first==null){
                           first=new node<T>(item);
                           current=first;
                   }
                   else{
                           current.next = new node<T>(item);
                           current=current.next;
                   }
           }
           public void start(){ current=first; }
           public void next(){ current=current.next; }
   }
   public class main{
           public static void Main(){
                   list<int> a = new list<int>();
                   a.push(1);
                   a.push(2);
                   a.push(3);
                   for( a.start(); a.current != null; a.next()){
                           WriteLine(a.current.item);
                   } } }