Removing and shifting remaining elements in an array C++ - c++

Question

List.cpp (class definitions)
I have been working on code that is suppose to help familiarize with classes. My code currently has a function that displays a menu of options for the users. Option [1] is suppose to add a string, option [2] is suppose to remove a string from the list, option [3] prints the string list, option [4] exits. My option [1] seems to work okay as the user is able to input one string at a time but I am having a hard time with the removal of a string. The strings are currently stored in an array of 10 elements. I believe the function I wrote for the string removal is okay as I have debugged it and it seems successful, however, I am not seeing results on my console window.
My array is located in a private class in my class: string items[MAX_ITEMS]; along with another variable called: int totalItems;
The class is then called in my main function using a switch case:
//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;
}

Answer 1

Here is how you code should probably look:
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;
}
If you would like to make your code more efficient, I can give you more suggestions on how to do it. This above should answer your question.
Also using an array for a struct like this isn't optimal at all. Using linked listed would mean no shifting would be required.
Edit: replaced long text with a code example
Edit2: added return statement if shifting is no longer necessary

Answer 2

FOR me it's unclear what you want to do as unavailability of full code to run.
But I think this should work as of what I think yo want to do
bool List::remove(const string& data){
for (int i = 0; i < totalItems; i++)
{
if (items[i] == data)
{
for (int j = i; j < totalItems-1; j++)
{
items[j] = items[j+1];
}
totalItems--;
return true;
}
}
return false;

Answer 3

if (inList(data) == true || data.empty() == true)
{
return false;
}
If the data parameter is in your list object, you return without removing anything? this should be !inList(data)
Additionally, when you make it into the loop below this code this loop:
for (int j = i; j < MAX_ITEMS; j++)
{
items[j] = items[j + 1];
items[MAX_ITEMS - 1] == " ";
break;
}
will only execute for j=i, the "break" statement will stop execution of this inner loop, and go back to the outer loop.
EDIT: this is how I personally would go about this problem.
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;
}