代写C++基础作业，练习Struct的用法。

Objectives

After this lab assignment, students should be able to:

• Declare and initialize C++ structs
• Implement designs using structs

Instructions

In this lab, we will create an abstraction of a vending machine in C++, using structs to describe each item in the machine, and a vector to maintain a list of all the items in the machine.
Use the following struct declaration for vending machine items:

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struct item {
  string name; // name of the item
  int code;    // numerical code entered to select the item
  float price; // price per unit of the item
  int stock;   // number of items available in the machine
};

Use the following vector declaration for the vending machine:

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int main() {
  vector<item> vendingMachine;

Complete the three following function headers shown below:

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float totalValue(vector<item> vendingMachine)
// return the total value of all items in the vending machine

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void stock(string name, int count, vector<item> &vendingMachine)
// add "count" items to the vending machine with the given "name"
// if the item to be added was not already in the machine, prompt the user for its code and price (in dollars)
// if the code is already being used by the machine, prompt the user for a different code

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void purchase(float balance, int code, vector<item> &vendingMachine)
// make a purchase from the vending machine
// "balance" is the amount of money (in dollars) inserted
// "code" is the item to purchase
// if "code" is not mapped to an item, display error message
// if the item is more expensive than "balance", display error message
// if purchase is successful, display change to be returned in dollars and update the stock of that item.

Testing the Functions

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int main() {
  vector<item> vendingMachine;
  stock("Doublemint Gum", 1, vendingMachine);
  cout << "-------------------" << endl;
  purchase(.50, 100, vendingMachine);
  cout << "-------------------" << endl;
  stock("Chocolate Chip Cookies", 10, vendingMachine);
  cout << "-------------------" << endl;
  stock("Chocolate Chip Cookies", 5, vendingMachine);
  cout << "-------------------" << endl;
  purchase(.75, 100, vendingMachine);
  cout << "-------------------" << endl;
  purchase(1.00, 100, vendingMachine);
  cout << "This vending machine now has $" totalValue(vendingMachine) << fixed << setprecision(2) << " worth of items" << endl;
}

Sample Output

The item you are adding, Doublemint Gum, was not in the machine.Please enter the following information for this itemCode: 100Price: $0.75You have added 1 units of Doublemint Gum. Now there are 1 units in the machine------------------You have selected to purchase Doublemint Gum, which costs $0.75Your balance is $0.50. Not enough money!------------------The item you are adding, Chocolate Chip Cookies, was not in the machine.Please enter the following information for this itemCode: 100That code is already being used by Doublemint Gum.Enter a new code:101Price: $2.00You have added 10 units of Chocolate Chip Cookies. Now there are 10 units in the machine------------------You have added 5 units of Chocolate Chip Cookies. Now there are 15 units in the machine------------------You have selected to purchase Doublemint Gum, which costs $0.75Thank you for purchasing! Your change is: $0.00------------------Item not found!------------------This vending machine now has $30.00 worth of itemsPress any key to continue ...

Submission

Call your program VendingMachine.cpp. This file must contain all of the following items:

• Completed function definitions:
  • totalValue()
  • purchase()
  • stock()
• Declaration of struct item
• main() function with same code found in the Testing the Functions section above
• A sample output of your program, like shown in the Sample Output section above (the output does not have to match exactly)

Submit VendingMachine.cpp to Canvas before the deadline.