我可以在 C++ 中使数组的某些值不可更改吗？

Question

I am designing a console-based Sudoku. According to the game, you can change entries as you move along the board. I've used a 2d array to store the values but the problem here is that I cannot make some of the entries constant as in the sudoku game where some values on the board cannot be changed so the user must reach a solution following those entries. So my question is:

- How can I make some of the entries constant here?

I have attached the code below

#include <windows.h>
#include <iostream>
#include <conio.h>
using namespace std;

#define KEY_UP 72
#define KEY_DOWN 80
#define KEY_LEFT 75
#define KEY_RIGHT 77

class Sudoku
{
    int wholeArray[9][9];
    int number;

public:
    void setArray(void);
    void displayArray(int& x, int& y);
    void readNumber(void);
    void setPositions(int& x, int& y);
    void changeEntry(int &x, int &y);
};

void setConsoleColor(int textColor, int bgColor) {
    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), (textColor + (bgColor * 16)));
}

void Sudoku::setArray(void)
{
    for (int i = 0; i < 9; i++)
    {
        for (int j = 0; j < 9; j++)
        {
            wholeArray[i][j] = 0;
        }
    }
}

void Sudoku::displayArray(int& x, int& y)
{
    setConsoleColor(11, 0);
    cout << "\t\b\b\b1 2 3   4 5 6   7 8 9\n";
    cout << "   -------------------------\n";
    for (int i = 0; i < 9; i++)
    {
        cout << i + 1 << "  | ";
        for (int j = 0; j < 9; j++)
        {
            if (x == i && y == j)
                setConsoleColor(0, 11);
            cout << wholeArray[i][j];
            setConsoleColor(11, 0);
            cout << " ";

            if ((j + 1) % 3 == 0)
                cout << "| ";
        }
        cout << endl;
        if ((i + 1) % 3 == 0)
            cout << "   -------------------------\n";
    }
}

void Sudoku::readNumber(void)
{
    cout << "Enter number you want to enter (from 1-9): ";
    cin >> number;
}

void Sudoku::setPositions(int& x, int& y)
{
        char key = _getch();
        if (key == KEY_UP)
            x--;
        if (key == KEY_DOWN)
            x++;
        if (key == KEY_LEFT)
            y--;
        if (key == KEY_RIGHT)
            y++;

        if (x < 0)
            x = 8;
        else if (x > 8)
            x = 0;

        if (y < 0)
            y = 8;
        else if (y > 8)
            y = 0;

        if (key == 'x')
            exit(0);
        if (key == 'v')
            changeEntry(x, y);
        system("cls");
}

void Sudoku:: changeEntry(int& x, int& y)
{
    int entry;
    do
    {
        cout << "Enter value:\t";
        cin >> entry;
    } while (entry < 1 || entry > 9);

    wholeArray[x][y] = entry;
}

int main()
{
    int x = 0, y = 0, entry;

    Sudoku s1;
    s1.setArray();

    s1.displayArray(x, y);
    while (1)
    {
        s1.setPositions(x, y);
        s1.displayArray(x, y);
    }
    return 0;
}

Answer 1

Can I make some values of an array unchangeable in c++?

You can make an entire array unchangeable by making it an array of const objects. You can make an array entirely changeable by making it an array of non-const objects. C++ arrays are homogeneous, so you cannot have mix of differently qualified types.

What you could have is an array of std::variant<T, const T> . Or, you could simply write a class that wraps the array that allows modification only through member functions. Those member functions can refuse to change elements that you deem to be unchangeable.

Answer 2

You can create another array forbidden[9][9] and the position that you don't want the user to change mark them for example

forbidden[1][0] = 1;
forbidden[2][5] = 1;
forbidden[3][7] = 1;

and when you want to change the value of your original array check the forbidden array first

if (key == 'v' && forbidden[x][y] != 1)
    changeEntry(x, y);