Question

C++ Class involving difference.

The goal is to overload the function:

void Bag::operator-=(const Bag& a_bag)

// The Set Difference between two sets A and B is the set that consists of the elements of A which are not elements of B. Bag bag1 = (1,2,3) and Bag bag2 = (2,4,5) then bag1-=bag2 should return 1,3,4,5.

//parameter a_bag to be subtracted from this (the calling) bag

//post removes all data from items_ that is also found in a_bag

//Since type is void, it should not return an array.

#include <iostream>
#include <string>

#include <vector>

using namespace std;

template
class Bag
{
public:
    Bag();
    int getCurrentSize() const;
    bool isEmpty() const;
    bool add(const T& new_entry);
    bool remove(const T& an_entry);
    /**
     @post item_count_ == 0
     **/
    void clear();
    /**
     @return true if an_etry is found in items_, false otherwise
     **/
    bool contains(const T& an_entry) const;

    /**
     @return the number of times an_entry is found in items_
     **/
    int getFrequencyOf(const T& an_entry) const;

    /**
     @return a vector having the same cotntents as items_
     **/
    std::vector toVector() const;

    void display() const;  // displays the output 

    void operator-=(const Bag& a_bag); //DO NOT CHANGE RETURN TYPE

protected:
    static const int DEFAULT_CAPACITY = 200;  //max size of items_
    T items_[DEFAULT_CAPACITY];              // Array of bag items
    int item_count_;                         // Current count of bag items
    int getIndexOf(const T& target) const;


};

template
Bag::Bag(): item_count_(0)
{
}  // end default constructor

template
int Bag::getCurrentSize() const
{
    return item_count_;
}  // end getCurrentSize

template
bool Bag::isEmpty() const
{
    return item_count_ == 0;
}  // end isEmpty


template
bool Bag::add(const T& new_entry)
{
    bool has_room = (item_count_ < DEFAULT_CAPACITY);
    //bool notDup = items_.getFrequencyOf(new_entry) == 0; 
    if (has_room) //&& notDup) 
    {
        items_[item_count_] = new_entry;
        item_count_++;
        return true;
    }  // end if

    return false;
}  // end add

template
void Bag::display() const {
    for(int x = 0; x < item_count_;x++)
        cout << items_[x] << ", "; 
}


/**
 @return true if an_entry was successfully removed from items_, false otherwise
 **/
template
bool Bag::remove(const T& an_entry)
{
   int found_index = getIndexOf(an_entry);
    bool can_remove = !isEmpty() && (found_index > -1);
    if (can_remove)
    {
        item_count_--;
        items_[found_index] = items_[item_count_];
    }  // end if

    return can_remove;
}  // end remove


/**
 @post item_count_ == 0
 **/
template
void Bag::clear()
{
    item_count_ = 0;
}  // end clear

template
int Bag::getFrequencyOf(const T& an_entry) const
{
   int frequency = 0;
   int cun_index = 0;       // Current array index
   while (cun_index < item_count_)
   {
      if (items_[cun_index] == an_entry)
      {
         frequency++;
      }  // end if

      cun_index++;          // Increment to next entry
   }  // end while

   return frequency;
}  // end getFrequencyOf

template
bool Bag::contains(const T& an_entry) const
{
    return getIndexOf(an_entry) > -1;
}  // end contains

template
std::vector Bag::toVector() const
{
   std::vector bag_contents;
    for (int i = 0; i < item_count_; i++)
        bag_contents.push_back(items_[i]);

   return bag_contents;
}  // end toVector

template
void Bag::operator-=(const Bag& a_bag)

{}

Answer 1

template
void Bag::operator-=(const Bag& a_bag){
    
    for(int i=item_count_; i>=0; i--) {
        T x = items_[i];
        
        if(a_bag.contains(x)) {
            remove(x);
        } else {
            add(x);
        }
    }
    
}

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