The function removeAt of the class arrayListType removes an element from the lis

Question

The function removeAt of the class arrayListType removes an element from the list by shifting the elements of the list. However, if the element to be removed is at the beginning of the list and the list is fairly large it could take a lot of computer time. Because the list elements are in no particular order, you could simply remove the element by swapping the last element of the list with the item to be removed and reducing the length of the list. Rewrite the definition of the function removeAt using this technique.

#ifndef H_arrayListType
#define H_arrayListType

class arrayListType
{
public:
    bool isEmpty() const;
      //Function to determine whether the list is empty
      //Postcondition: Returns true if the list is empty;
      //               otherwise, returns false.

    bool isFull() const;
      //Function to determine whether the list is full
      //Postcondition: Returns true if the list is full;
      //               otherwise, returns false.

    int listSize() const;
      //Function to determine the number of elements in
      //the list.
      //Postcondition: Returns the value of length.

    int maxListSize() const;
      //Function to determine the maximum size of the list
      //Postcondition: Returns the value of maxSize.

    void print() const;
      //Function to output the elements of the list
      //Postcondition: Elements of the list are output on the
      //               standard output device.

    bool isItemAtEqual(int location, int item) const;
      //Function to determine whether item is the same as
      //the item in the list at the position specified
      //by location.
      //Postcondition: Returns true if list[location]
      //               is the same as item; otherwise,
      //               returns false.
      //               If location is out of range, an
      //               appropriate message is displayed.

    virtual void insertAt(int location, int insertItem) = 0;
      //Function to insert insertItem in the list at the
      //position specified by location.
      //Note that this is an abstract function.
      //Postcondition: Starting at location, the elements of
      //               the list are shifted down,
      //               list[location] = insertItem; length++;  
      //               If the list is full or location is out of
      //               range, an appropriate message is displayed.

    virtual void insertEnd(int insertItem) = 0;
      //Function to insert insertItem an item at the end of
      //the list. Note that this is an abstract function.
      //Postcondition: list[length] = insertItem; and length++;
      //               If the list is full, an appropriate
      //               message is displayed.

    void removeAt(int location);
      //Function to remove the item from the list at the
      //position specified by location
      //Postcondition: The list element at list[location] is
      //               removed and length is decremented by 1.
      //               If location is out of range, an
      //               appropriate message is displayed.

    void retrieveAt(int location, int& retItem) const;
      //Function to retrieve the element from the list at the
      //position specified by location
      //Postcondition: retItem = list[location]
      //               If location is out of range, an
      //               appropriate message is displayed.

    virtual void replaceAt(int location, int repItem) = 0;
      //Function to replace the elements in the list
      //at the position specified by location.
      //Note that this is an abstract function.
      //Postcondition: list[location] = repItem
      //               If location is out of range, an
      //               appropriate message is displayed.

    void clearList();
      //Function to remove all the elements from the list
      //After this operation, the size of the list is zero.
      //Postcondition: length = 0;

    virtual int seqSearch(int searchItem) const = 0;
      //Function to search the list for searchItem.
      //Note that this is an abstract function.
      //Postcondition: If the item is found, returns the
      //               location in the array where the item is
      //               found; otherwise, returns -1.

    virtual void remove(int removeItem) = 0;
      //Function to remove removeItem from the list.
      //Note that this is an abstract function.
      //Postcondition: If removeItem is found in the list,
      //               it is removed from the list and length
      //               is decremented by one.

    arrayListType(int size = 100);
      //Constructor
      //Creates an array of the size specified by the
      //parameter size. The default array size is 100.
      //Postcondition: The list points to the array, length = 0,
      //               and maxSize = size;

    arrayListType (const arrayListType& otherList);
       //Copy constructor

    virtual ~arrayListType();
      //Destructor
      //Deallocate the memory occupied by the array.

protected:
    int *list;    //array to hold the list elements
    int length;   //variable to store the length of the list
    int maxSize; //variable to store the maximum
                  //size of the list
};

#endif

#include <iostream>
#include "arrayListType(3).h"

using namespace std;

bool arrayListType(3)::isEmpty() const
{
    return (length == 0);
} //end isEmpty

bool arrayListType(3)::isFull() const
{
    return (length == maxSize);
} //end isFull

int arrayListType(3)::listSize() const
{
   return length;
} //end listSize

int arrayListType(3)::maxListSize() const
{
   return maxSize;
} //end maxListSize

void arrayListType(3)::print() const
{
    for (int i = 0; i < length; i++)
        cout << list[i] << " ";
    cout << endl;
} //end print

bool arrayListType(3)::isItemAtEqual(int location, int item) const
{
    if (location < 0 || location >= length)
    {
        cout << "The location of the item to be removed "
             << "is out of range." << endl;

        return false;
    }
    else
        return (list[location] == item);
} //end isItemAtEqual

void arrayListType(3)::removeAt(int location)
{
    if (location < 0 || location >= length)
        cout << "The location of the item to be removed "
             << "is out of range." << endl;
    else
    {
        for (int i = location; i < length - 1; i++)
            list[i] = list[i+1];

        length--;
    }
} //end removeAt

void arrayListType(3)::retrieveAt(int location, int& retItem) const
{
    if (location < 0 || location >= length)
        cout << "The location of the item to be retrieved is "
             << "out of range" << endl;
    else
        retItem = list[location];
} //end retrieveAt

void arrayListType(3)::clearList()
{
    length = 0;
} //end clearList

arrayListType(3)::arrayListType(3)(int size)
{
    if (size <= 0)
    {
        cout << "The array size must be positive. Creating "
             << "an array of the size 100." << endl;

        maxSize = 100;
    }
    else
        maxSize = size;

    length = 0;

    list = new int[maxSize];
} //end constructor

arrayListType(3)::~arrayListType(3)()
{
    delete [] list;
} //end destructor

arrayListType(3)::arrayListType(3)(const arrayListType& otherList)
{
    maxSize = otherList.maxSize;
    length = otherList.length;

    list = new int[maxSize];    //create the array

    for (int j = 0; j < length; j++) //copy otherList
        list [j] = otherList.list[j];
}//end copy constructor

Explanation / Answer

void arrayListType(3)::removeAt(int location)
{
    if (location < 0 || location >= length)
        cout << "The location of the item to be removed "
             << "is out of range." << endl;
    else
    {
  
            list[location] = list[length-1];

//just swap last item in list with item in location

//then reduce the length of list

//so the item which is now in last location gets removed

        length--;
    }
} //end removeAt

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