My second last value is garbage,the program is about calculating sum - c++

Question

#include <iostream>
using namespace std;
int main()
{
int oldsize;
string choice;
cout << "Welcome to the Walmart Calculation Center!";
cout << endl;
cout << "Enter the Number of Items" << endl;
cin >> oldsize;
int* items = new int[oldsize];
for (int i = 0; i < oldsize; i++)
{
cout << "ENTER THE PRICE OF ITEM" << i + 1 << "!" << endl;
cin >> items[i];
}
cout << "Do you want to add more items? (YES OR NO)" << endl;
cin >> choice;
if (choice == "YES")
{
int newbie;
int newsize;
int total = 0;
while (choice == "YES")
{
newsize = oldsize + 1;
int* Nitems = new int[newsize];
for (int i = 0; i < oldsize; i++)
{
Nitems[i] = items[i];
}
cout << "Enter the Price of New ITEM!" << endl;
cin >> newbie;
Nitems[oldsize] = newbie;
oldsize = newsize;
cout << "Do you want to add more items? (YES OR NO)" << endl;
cin >> choice;
if (choice=="NO")
{
for (int i = 0; i < newsize; i++)
{
cout << Nitems[i] << endl;
}
}
}
}
}
This program is about calculating sum of the bill at a store. and ask user that if he/she wants to enter any other item, until he/she says no. In the end it displays the total bill.

Answer 1

You never change items array, but you change oldsize variable which represents it's size. When you the try to copy items from items to Nitems, you go out of bounds of items array (because oldsize is bigger that actual size of array).
The simplest fix would be to repoint items to Nitems at the same moment when you change the size.
while (choice == "YES")
{
newsize = oldsize + 1;
int* Nitems = new int[newsize];
for (int i = 0; i < oldsize; i++)
{
Nitems[i] = items[i];
}
cout << "Enter the Price of New ITEM!" << endl;
cin >> newbie;
Nitems[oldsize] = newbie;
oldsize = newsize;
items = Nitems; //here
cout << "Do you want to add more items? (YES OR NO)" << endl;
cin >> choice;
if (choice=="NO")
{
for (int i = 0; i < newsize; i++)
{
cout << Nitems[i] << endl;
}
}
}
See the line marked with comment? It makes items pointer point to the same array as Nitems. There is no copying involved, if you change items[1], Nitems[1] would see the same change. But having two pointers to the same array let's you keep the current array when you create new array in the next iteration.
There is of course problem with memory leaks, but don't worry too much about that until you learn how to manage memory properly. Badly placed delete is much worse that memory leak (especially in such small programs).
And of course, your code would be much simpler if you used std::vector:
std::vector<int> items;
while (choice == "YES")
{
cout << "Enter the Price of New ITEM!" << endl;
cin >> newbie;
items.push_back(newbie);
cout << "Do you want to add more items? (YES OR NO)" << endl;
cin >> choice;
if (choice=="NO")
{
for (int i = 0; i < items.size(); i++)
{
cout << items[i] << endl;
}
}
}

Answer 2

I am unable to comment due to low reputation. But I feel you are still unclear about dynamic allocation concepts. You will need to delete if you create something using new to avoid memory leaks. This program can be much simpler like below. I still use new deliberately to show the delete scenario. Apart from that you also need to clear up some basics as given in comments. All the best!
#include <iostream>
using namespace std;
int main()
{
int oldsize, newbie;
int total=0;
string choice;
cout << "Welcome to the Walmart Calculation Center!";
cout << endl;
cout << "Enter the Number of Items" << endl;
cin >> oldsize;
int* items = new int[oldsize];
for (int i = 0; i < oldsize; i++)
{
cout << "ENTER THE PRICE OF ITEM" << i + 1 << "!" << endl;
cin >> items[i];
total+=items[i];
}
do {
cout << "Do you want to add more items? (YES OR NO)" << endl;
cin >> choice;
//if user inputs NO, break out of do while.
if(choice == "NO") break;
//continue here if YES
cout << "Enter the Price of New ITEM!" << endl;
cin >> newbie;
total+=newbie;
}while(choice=="YES");
cout << "Total: " << total << endl;
delete[] items;
}