如何使用Visual Studio在C ++中使用2D数组？

Question

I'm new to this site and programming in C++ language this semester.

I have been really trying for 2 days and have asked classmates but they do not know either. A classmate said to use the 2D arrays but I don't know what that is and my professor has not gone over 2D arrays.

I am stuck and would really appreciate help.

The input file contains this:

Plain_Egg 1.45
Bacon_and_Egg 2.45
Muffin 0.99
French_Toast 1.99
Fruit_Basket 2.49
Cereal 0.69
Coffee 0.50
Tea 0.75

idk how to display all the "users" orders

Basically a receipt, like he orders this and how many, then ask "u want anything else?", then take the order number and how many again, THEN at the end give back a receipt that looks like this

bacon_and_eggs    $2.45
Muffin            $0.99
Coffee            $0.50
Tax               $0.20
Amount Due        $4.14

Here is my code:

// Libraries

#include <iostream>
#include <string>
#include <iomanip>
#include <fstream>
#include <cmath>

using namespace std;

//structures

struct menuItemType {
    string itemName;
    double itemCost;
};


// Prototypes
void header();
void readData(menuItemType menu[]);
void Display(menuItemType menu[]);

int main() {

    header();
    menuItemType menu [8];
    readData(menu); 
    Display(menu);

    //system("pause");

    return 0;
}

void header() {
    char c= 61;
    for (int i=0; i < 64; i++) {
        cout << c; 
}

cout << c << endl; 
cout << endl;
cout << "Breakfast Menu" <<endl;


    for (int i=0; i < 64; i++) {
        cout << c; 
    }

    cout << "" << c << endl;
    cout << endl;
}

void readData(menuItemType item[]) {
    int i=0;
    ifstream in;
    in.open("input.txt");
    cout << fixed << setprecision(2);

    while(!in.eof()) {
        in >> item[i].itemName >> item[i].itemCost;
        ++i;
    }
}

void Display(menuItemType item[]) {
    int choice = 0, quantity = 0;
    double total = 0.0, totalF = 0.0, tax = 0.0;
    char exit = 'y';
    int j = 1, z = 1, i = 1;

    //the Menu
    for (int i=0; i<8; i++){
        cout << j << ". " << setw(18) << left << item[i].itemName << "$" << setw(10) << item[i].itemCost << endl;
        j++;
    }

    cout << endl;

    while(exit == 'y' || exit == 'Y') {

        cout << "Please Enter your Selection or 0 to Exit : ";
        cin >> choice;

        if(cin.fail()) {
            cout << "*******Invalid selection*******" << endl;
            cin.clear();
            cin.ignore(1000,'\n');
        } else if (choice==0) {break; }
        else {
            cout<< "Enter Quantity: ";
            cin>> quantity;

            if (quantity==0) { break;}
            else {
                choice--;
                total += (quantity * item[choice].itemCost);
                tax = (total * .05);
                totalF = total + tax;
                cout << endl;
            }
            cout << endl;
            cout << "======================================================" << endl;
            cout << item[choice].itemName << "\t\t" << item[choice].itemCost << endl;
            cout << "======================================================" << endl;
            cout << "Do you want to continue (Y/N): ";
            cin >> exit;
        }
    }
}

Answer 1

First off, you don't need a two dimensional array for this! You already have a one dimensional array of a suitable structure, as far as I can tell: Something which stores the name of the object and its price. What is somewhat missing is how many objects are currently in the array and how much space it has. If you want to go with the content of the entire array, make sure that you objects are correctly initialized, eg, that the names are empty (this happens automatically, actually) and that the prices are zero (this does not).

I'm not sure if it is a copy&paste errors but the headers are incorrectly included. The include directives should look something like this:

#include <iostream>

The actual loop reading the values doesn't really work: You always need to check that the input was successful after you tried to read! Also, using eof() for checking that the loop ends is wrong (I don't know where people pick this up from; any book recommending the use of eof() for checking input loops is only useful for burning). The loop should look something like this:

while (i < ArraySize && in >> item[i].itemName >> item[i].itemCost)
    ++i;
}

This also fixes the potential boundary overrun in case there is more input than the array can consume. You might want to consider using a std::vector<Item> instead: this class keeps track of how many elements there are and you can append new elements as needed.

Note that you didn't quite say what you are stuck with: You'd need to come up with a clearer description of what your actual problem is. The above is just correcting existing errors and readjusting the direction to look into (ie, forget about two dimensional arrays for now).