我需要创建一个Union函数，该函数将生成两个包的并集。我的问题是，当我运行该程序时，该函数将添加元素，有时如果多次输入，它可能会重复相同的数字。如何改善此功能，使号码仅出现一次？
#pragma once
// Created by Frank M. Carrano and Tim Henry.
// Copyright (c) 2013 Pearson Education. All rights reserved.
/** Header file for an array-based implementation of the ADT bag.
@file ArrayBag.h */
#ifndef _ARRAY_BAG
#define _ARRAY_BAG
#include "BagInterface.h"
#include <cstddef>
template<class ItemType>
class ArrayBag : public BagInterface<ItemType>
{
private:
static const int DEFAULT_CAPACITY = 15; // Small size to test for a full bag
ItemType items[DEFAULT_CAPACITY]; // Array of bag items
int itemCount; // Current count of bag items
int maxItems; // Max capacity of the bag
// Returns either the index of the element in the array items that
// contains the given target or -1, if the array does not contain
// the target.
//int getIndexOf(const ItemType& target) const;
public:
ArrayBag();
int getIndexOf(const ItemType& target) const;
int getCurrentSize() const;
bool isEmpty() const;
bool add(const ItemType& newEntry);
bool remove(const ItemType& anEntry);
bool remove2(const ItemType& anEntry);
void clear();
bool contains(const ItemType& anEntry) const;
int getFrequencyOf(const ItemType& anEntry) const;
void displayBag2()const;
vector<ItemType> toVector() const;
ArrayBag<ItemType> Union(const ArrayBag<ItemType> myBag2);
ArrayBag<ItemType> Intersection(const ArrayBag<ItemType> myBag2);
ArrayBag<ItemType> Difference(const ArrayBag<ItemType> myBag2);
}; // end ArrayBag
// Created by Frank M. Carrano and Tim Henry.
// Copyright (c) 2013 Pearson Education. All rights reserved.
/** Implementation file for the class ArrayBag.
@file ArrayBag.cpp */
#include "ArrayBag.h"
#include <cstddef>
template<class ItemType>
ArrayBag<ItemType>::ArrayBag() : itemCount(0), maxItems(DEFAULT_CAPACITY)
{
} // end default constructor
template<class ItemType>
int ArrayBag<ItemType>::getCurrentSize() const
{
return itemCount;
} // end getCurrentSize
template<class ItemType>
bool ArrayBag<ItemType>::isEmpty() const
{
return itemCount == 0;
} // end isEmpty
template<class ItemType>
bool ArrayBag<ItemType>::add(const ItemType& newEntry)
{
bool hasRoomToAdd = (itemCount < maxItems);
if (hasRoomToAdd)
{
items[itemCount] = newEntry;
itemCount++;
} // end if
return hasRoomToAdd;
} // end add
/*
template<class ItemType>
bool ArrayBag<ItemType>::remove(const ItemType& anEntry)
{
return false; // STUB
} // end remove
*/
template<class ItemType>
bool ArrayBag<ItemType>::remove(const ItemType& anEntry)
{
int locatedIndex = getIndexOf(anEntry);
bool canRemoveItem = !isEmpty() && (locatedIndex > -1);
if (canRemoveItem)
{
itemCount--;
items[locatedIndex] = items[itemCount];
} // end if
return canRemoveItem;
} // end remove
template<class ItemType>
bool ArrayBag<ItemType>::remove2(const ItemType& anEntry)
{
int locatedIndex = getIndexOf(anEntry);
bool canRemoveItem = !isEmpty() && (locatedIndex > -1);
if (canRemoveItem)
{
for (int i = 0; i < getCurrentSize(); i++)
{
if (items[i] == anEntry)
{
for (int j = i; j < (getCurrentSize() - 1); j++)
{
items[j] = items[j + 1];
}
itemCount--;
}
}
//items[locatedIndex] = items[itemCount];
} // end if
return canRemoveItem;
} // end remove
/*
// STUB
template<class ItemType>
void ArrayBag<ItemType>::clear()
{
// STUB
} // end clear
*/
template<class ItemType>
void ArrayBag<ItemType>::clear()
{
itemCount = 0;
} // end clear
template<class ItemType>
int ArrayBag<ItemType>::getFrequencyOf(const ItemType& anEntry) const
{
int frequency = 0;
int curIndex = 0; // Current array index
while (curIndex < itemCount)
{
if (items[curIndex] == anEntry)
{
frequency++;
} // end if
curIndex++; // Increment to next entry
} // end while
return frequency;
} // end getFrequencyOf
template<class ItemType>
bool ArrayBag<ItemType>::contains(const ItemType& anEntry) const
{
return getIndexOf(anEntry) > -1;
} // end contains
/* ALTERNATE 1: First version
template<class ItemType>
bool ArrayBag<ItemType>::contains(const ItemType& target) const
{
return getFrequencyOf(target) > 0;
} // end contains
// ALTERNATE 2: Second version
template<class ItemType>
bool ArrayBag<ItemType>::contains(const ItemType& anEntry) const
{
bool found = false;
int curIndex = 0; // Current array index
while (!found && (curIndex < itemCount))
{
if (anEntry == items[curIndex])
{
found = true;
} // end if
curIndex++; // Increment to next entry
} // end while
return found;
} // end contains
*/
template<class ItemType>
vector<ItemType> ArrayBag<ItemType>::toVector() const
{
vector<ItemType> bagContents;
for (int i = 0; i < itemCount; i++)
bagContents.push_back(items[i]);
return bagContents;
} // end toVector
// private
template<class ItemType>
int ArrayBag<ItemType>::getIndexOf(const ItemType& target) const
{
bool found = false;
int result = -1;
int searchIndex = 0;
// If the bag is empty, itemCount is zero, so loop is skipped
while (!found && (searchIndex < itemCount))
{
if (items[searchIndex] == target)
{
found = true;
result = searchIndex;
}
else
{
searchIndex++;
} // end if
} // end while
return result;
} // end getIndexOf
template<class ItemType>
void ArrayBag<ItemType>::displayBag2()const
{
cout << "The bag contains: < ";
for (int i = 0; i < getCurrentSize(); i++)
{
cout << items[i] << " ";
}
cout << ">";
} // end displayBag
template <class ItemType>
ArrayBag<ItemType> ArrayBag <ItemType> ::Union(const ArrayBag<ItemType> bag2)
{
ArrayBag<ItemType> unionBag;
for (int i = 0; i < getCurrentSize(); i++)
{
unionBag.add(items[i]);
}
for (int i = 0; i < bag2.getCurrentSize(); i++)
{
unionBag.add(bag2.items[i]);
if (items[i] == bag2.items[i])
unionBag.remove(bag2.items[i]);
}
return unionBag;
}
template <class ItemType>
ArrayBag<ItemType> ArrayBag<ItemType>::Intersection(const ArrayBag<ItemType> bag2)
{
ArrayBag<ItemType> interBag;
for (int i = 0; i < getCurrentSize(); i++)
{
if (bag2.contains(items[i]))
interBag.add(items[i]);
}
return interBag;
}
template<class ItemType>
ArrayBag<ItemType> ArrayBag<ItemType>::Difference(const ArrayBag<ItemType> bag2)
{
ArrayBag<ItemType> diffBag;
for (int i = 0; i < getCurrentSize(); i++)
{
if (!bag2.contains(items[i]))
diffBag.add(items[i]);
}
return diffBag;
}
#endif
#pragma once
// Created by Frank M. Carrano and Tim Henry.
// Copyright (c) 2013 Pearson Education. All rights reserved.
/** Listing 1-1.
@file BagInterface.h */
#ifndef _BAG_INTERFACE
#define _BAG_INTERFACE
#include <vector>
using namespace std;
template<class ItemType>
class BagInterface
{
public:
/** Gets the current number of entries in this bag.
@return The integer number of entries currently in the bag. */
virtual int getCurrentSize() const = 0;
/** Sees whether this bag is empty.
@return True if the bag is empty, or false if not. */
virtual bool isEmpty() const = 0;
/** Adds a new entry to this bag.
@post If successful, newEntry is stored in the bag and
the count of items in the bag has increased by 1.
@param newEntry The object to be added as a new entry.
@return True if addition was successful, or false if not. */
virtual bool add(const ItemType& newEntry) = 0;
/** Removes one occurrence of a given entry from this bag,
if possible.
@post If successful, anEntry has been removed from the bag
and the count of items in the bag has decreased by 1.
@param anEntry The entry to be removed.
@return True if removal was successful, or false if not. */
virtual bool remove(const ItemType& anEntry) = 0;
/** Removes all entries from this bag.
@post Bag contains no items, and the count of items is 0. */
virtual void clear() = 0;
/** Counts the number of times a given entry appears in bag.
@param anEntry The entry to be counted.
@return The number of times anEntry appears in the bag. */
virtual int getFrequencyOf(const ItemType& anEntry) const = 0;
/** Tests whether this bag contains a given entry.
@param anEntry The entry to locate.
@return True if bag contains anEntry, or false otherwise. */
virtual bool contains(const ItemType& anEntry) const = 0;
/** Empties and then fills a given vector with all entries that
are in this bag.
@return A vector containing all the entries in the bag. */
virtual vector<ItemType> toVector() const = 0;
}; // end BagInterface
#endif
#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include "ArrayBag.h"
using namespace std;
void displayBag(ArrayBag<string>& bag)
{
cout << "The bag contains " << bag.getCurrentSize() << " items:" << endl;
vector<string> bagItems = bag.toVector();
int numberOfEntries = (int)bagItems.size();
for (int i = 0; i < numberOfEntries; i++) {
cout << bagItems[i] << " ";
} // end for cout << endl << endl;
} // end displayBag
void bagTester(ArrayBag<string>& bag)
{
cout << "isEmpty: returns " << bag.isEmpty() << "; should be 1 (true)" << endl;
displayBag(bag);
string items[] = { "one", "two", "three", "four", "five", "one" };
cout << "Add 6 items to the bag: " << endl; for (int i = 0; i < 6; i++) { bag.add(items[i]); } // end for
displayBag(bag);
cout << "isEmpty: returns " << bag.isEmpty() << "; should be 0 (false)" << endl;
cout << "getCurrentSize: returns " << bag.getCurrentSize() << "; should be 6" << endl;
cout << "Try to add another entry: add(\"extra\") returns " << bag.add("extra") << endl;
} // end bagTester
int main()
{
ArrayBag<int> bag1, bag2;
char answer, answer2;
int n, n2;
cout << "How many numbers are going to be entered: ";
cin >> n;
for (int i = 0; i < n; i++)
{
int num;
cout << "Enter a number: ";
cin >> num;
bag1.add(num);
}
cout << endl;
bag1.displayBag2();
cout << endl;
cout << "The bag contains: " << bag1.getCurrentSize() << " numbers.";
cout << endl << endl;
cout << "Now we are going to create another bag for comparison." << endl;
cout << "How many numbers are going to be entered: ";
cin >> n2;
for (int i = 0; i < n2; i++)
{
int num;
cout << "Enter a number: ";
cin >> num;
bag2.add(num);
}
cout << endl;
bag2.displayBag2();
cout << endl;
cout << "The bag contains: " << bag2.getCurrentSize() << " numbers.";
cout << endl << endl;
cout << "The union of both bags is: " << endl;
ArrayBag<int> bag3 = bag1.Union(bag2);
bag3.displayBag2();
cout << endl;
cout << "The intersection of both bags is: " << endl;
ArrayBag<int> bag4 = bag1.Intersection(bag2);
bag4.displayBag2();
cout << endl;
cout << "The difference of both bags is: " << endl;
ArrayBag<int> bag5 = bag1.Difference(bag2);
bag5.displayBag2();
cout << endl;
cout << "The frequency of the number 4 is: " << bag1.getFrequencyOf(4);
cout << endl;
cout << "The index of the number 9 is: " << bag1.getIndexOf(9);
cout << endl << endl;
cout << "Now we are going to remove 4" << endl << endl;
for (int a = 0; a < n; a++)
{
bag1.remove2(4);
}
bag1.displayBag2();
cout << endl;
cout << "The bag contains: " << bag1.getCurrentSize() << " numbers.";
cout << endl << endl;
cout << "Would you like to remove another number (Y/N)? ";
cin >> answer;
if (answer == 'Y' || answer == 'y')
{
int remove;
cout << endl;
cout << "Which number would you like to remove: ";
cin >> remove;
for (int a = 0; a < n; a++)
{
bag1.remove2(remove);
}
cout << endl;
bag1.displayBag2();
}
else
bag1.displayBag2();
cout << endl;
cout << "Would you like to add more numbers to the bag? (Y/N)";
cin >> answer2;
if (answer2 == 'Y' || answer2 == 'y')
{
int add, quantity;
cout << endl;
cout << "How many numbers would you like to add: ";
cin >> quantity;
for (int a = 0; a < quantity; a++)
{
cout << endl;
cout << "Which number would you like to add: ";
cin >> add;
bag1.add(add);
}
cout << endl;
bag1.displayBag2();
cout << endl;
cout << "The bag contains: " << bag1.getCurrentSize() << " numbers.";
cout << endl;
}
cout << endl;
cout << endl << "Good bye!" << endl << endl;
system("pause");
return 0;
} // end main
答案 0 :(得分：3)
if (items[i] == bag2.items[i])
仅当您在bag2中签入的项目在当前对象中以完全相同的索引存在 时，这才成立。
如果需要重复删除，则需要检查联合中的任何项是否与源中的项匹配。您也应该将此操作作为插入操作的一部分，以避免出现插入后删除的情况，并且可能应该对两个源（bag2 和< / em>当前对象）。就像这样：
template <class ItemType>
ArrayBag<ItemType> ArrayBag <ItemType> ::Union(const ArrayBag<ItemType> bag2) {
ArrayBag<ItemType> unionBag;
// Add my items, removing dupes.
for (int i = 0; i < getCurrentSize(); i++)
if (! unionBag.contains(bag2.items[i]))
unionBag.add(items[i]);
// Add other items, removing dupes.
for (int i = 0; i < bag2.getCurrentSize(); i++)
if (! unionBag.contains(bag2.items[i]))
unionBag.add(bag2.items[i]);
return unionBag;
}
如果您确实想要真实的集合行为（每个项目中只有一个），则可能要考虑至少在构造联合时使用使用集合而不是袋子的可能性。您可以将每个固定物品转移到袋子中。不论您尝试添加多少次，一个集合只有一个项目。
当然，有相反 （a）解释，将两个袋子合并，一个不涉及删除重复项。可以得出这样的论据，即 sets {1,2,3}和{2,3,4}的并集是：
{1,2,3} U {2,3,4} => {1,2,3,4}
这两个项目作为 bags 的并集应为：
{1,2,3} U {2,3,4} => {1,2,2,3,3,4}
毕竟，包只是对象的容器，并且您可以在包中包含多个对象。将一袋七个苹果放到另一个三袋苹果中，将给您一袋十个苹果，而不是一个，三个或四个（取决于如何去除重复的苹果）。
（a）有人会说“更明智”，但我不想侮辱听众：-）