List.cpp（类定义）
我一直在研究有助于熟悉类的代码。我的代码目前有一个功能，可以显示用户的选项菜单。选项[1]假设添加一个字符串，选项[2]假设从列表中删除一个字符串，选项[3]打印字符串列表，选项[4]退出。我的选项[1]似乎工作正常，因为用户可以一次输入一个字符串，但我很难删除字符串。字符串当前存储在10个元素的数组中。我相信我为删除字符串编写的函数是可以的，因为我已经调试它并且看起来很成功，但是，我没有在控制台窗口看到结果。
我的数组位于我的类中的私有类中：字符串项[MAX_ITEMS];以及另一个名为：int totalItems;
的变量然后使用switch case在我的main函数中调用该类：
//This code snippet below is located in a separate cpp file with main
cout << "Please enter the text you want to remove: " << endl;
cin >> userInput;
list1.remove(userInput);
////////////////////////////////////////////////////////////////////
//preprocessor directives
#include <iostream>
#include <string>
//header files
#include "list.h"
using namespace std;
List::List()
{
//clear array prior to starting (set everything to NULL)
for (int i = 0; i < MAX_ITEMS; i++)
{
items[i] = " ";
}
totalItems = 0;
}
//void List::init()
//{
// string items[MAX_ITEMS];
// totalItems = 0;
//}
bool List::insert(const string& data)
{
//verifies that string is not empty, not in the list, and not full
if (data.empty() == true || inList(data) == true || isFull() == true)
{
return false;
}
else
{
// items[isFull)] = data;
// totalItems++;
items[totalItems++] = data;
return true;
}
}
bool List::isEmpty() const
{
//runs through loop to verify array is empty
for (int i = 0; i < MAX_ITEMS; i++)
{
if (items[i].empty() != true)
{
return false;
}
}
return true;
}
//identifies whether the string is full or not
bool List::isFull() const
{
if (totalItems == MAX_ITEMS)
{
return true;
}
else
{
return false;
}
}
//identifies whether the string is already in the list or not
bool List::inList(const string& theList)
{
for (int i = 0; i < MAX_ITEMS; i++)
{
if (items[i] == theList)
{
return true;
}
}
return false;
}
bool List::remove(const string& data)
{
if (inList(data) == true || data.empty() == true)
{
return false;
}
for (int i = 0; i < MAX_ITEMS; i++)
{
if (items[i] == data)
{
items[i] == " ";
for (int j = i; j < MAX_ITEMS; j++)
{
items[j] = items[j + 1];
items[MAX_ITEMS - 1] == " ";
break;
}
}
}
totalItems--;
return true;
}
//prints list
void List::printList()
{
for (int i = 0; i < MAX_ITEMS; i++)
{
cout << i << items[i] << '\t';
}
}
list_test.cpp（main.cpp）
#include <iostream>
#include <string>
//header files
#include "list.h"
using namespace std;
//function prototypes
int showSelection();
int main()
{
List list1;
string userInput = "";
int userChoice;
// list1.init();
userChoice = showSelection();
while (userChoice != 4)
{
switch(userChoice)
{
case 1:
cout << "Please enter the text you want to add: " << endl;
cin >> userInput;
list1.insert(userInput);
/*if (list1.inList(userInput) == false)
{
cout << "Text is already entered in the list!" << endl;
}*/
if (list1.isFull() == true)
{
cout << "You have entered the MAXIMUM amount of elements!" << endl;
}
break;
case 2:
cout << "Please enter the text you want to remove: " << endl;
cin >> userInput;
list1.remove(userInput);
break;
case 3:
cout << "Printed list: " << endl;
list1.printList();
break;
}
userChoice = showSelection();
}
cout << "Goodbye. Please press enter to exit." << endl;
//TESTING PURPOSES FOR FUNCTIONS
cout << list1.insert(userInput) << endl;
cout << list1.isEmpty() << endl;
cout << list1.isFull() << endl;
cout << list1.inList(userInput) << endl;
return 0;
}
/* ===========================================
Name: showSelection
Desc: displays menu for user to choose options
for their inputted string(s).
Args: none
Retn: none
=========================================== */
int showSelection()
{
int userChoice;
bool exit = false;
while (exit == false)
{
cout << "\nTo select an option, please enter the corresponding number: " << endl;
cout << "[1] to add a string" << endl;
cout << "[2] to remove a string" << endl;
cout << "[3] to print a string" << endl;
cout << "[4] to exit" << endl << endl;
cin >> userChoice;
cout << "You entered option: " << userChoice << endl;
cout << '\n';
if (userChoice == 1 || userChoice == 2 || userChoice == 3 || userChoice == 4)
{
exit = true;
}
else
{
cout << "Invalid selection" << endl;
}
}`enter code here`
return userChoice;
}
答案 0 :(得分：1)
if (inList(data) == true || data.empty() == true)
{
return false;
}
如果数据参数在列表对象中，则返回时不删除任何内容？这应该是！inList（data）
此外，当你进入此代码下面的循环时，这个循环：
for (int j = i; j < MAX_ITEMS; j++)
{
items[j] = items[j + 1];
items[MAX_ITEMS - 1] == " ";
break;
}
只会执行j = i，＆＃34; break＆＃34;语句将停止执行此内部循环，并返回外部循环。
编辑：这就是我个人会解决这个问题的方法。
bool List::remove(const string& data)
{
bool retVal;
if (!inList(data) || data.empty())
{
retVal = false;
}
else{
for (int i = 0; i < MAX_ITEMS; i++)
{
if (items[i] == data)
{
items[i] = " ";
for (int j = i; j < (MAX_ITEMS - 1); j++)
{
items[j] = items[j + 1];
}
items[MAX_ITEMS-1] = " ";
}
}
totalItems--;
retVal = true;
}
return retVal;
}
答案 1 :(得分：1)
以下是您的代码应该如何显示：
bool List::remove(const string& data) {
// only check if the list is empty so you don't nececarily go through it
// you shoudn't ask here if the given string is in the list
// because you will search for it anyway just below
if (data.empty())
return false;
for (int i = 0; i < MAX_ITEMS; ++i) {
if (items[i] == data) { // now if it was found
items[i] = " "; // set it to your empty value
--totalItems; // prefix -- is faster then postfix one (no copy is created)
for (int j = i; j < MAX_ITEMS - 1; ++j) {
// stop at j < MAX_ITEMS - 1 because you wouldn't want
// to swap last element with the next because there
// is none behind it
if (items[j + 1] == " ")
// if the next item is already empty you don't need to shift any more
return true;
// swap the next item with much more
// efficient std::swap function
std::swap(items[j], items[j + 1]);
}
return true; // value is removed and items shifted so you can now return
}
}
// if function gets to this point that means the value wasn't found
return false;
}
如果您希望提高代码效率，我可以为您提供更多有关如何操作的建议。以上内容应该回答你的问题。
对这样的结构使用数组也不是最佳选择。使用链接列表意味着不需要转移。
编辑：用代码示例替换长文本 Edit2：如果不再需要转移，则添加return语句
答案 2 :(得分：1)
对我而言，由于无法运行完整代码，因此无法确定您要执行的操作。
但我认为这应该符合我的想法，你想做什么
dplyr