C++ Update console output

Question

I'm trying to make a program to print out a grid and given x and y co-ordinates change a value in the grid. For example, if the user entered X:0 and Y:0 it would change the value '9' in the image below to a predefined value (in this case I want to change the value 9 to 0).

My question is, is it possible to update the output of the console so that the '0' would override the '9' without printing out the entire grid again. I want to be able to do this multiple times.

If that is not possible, how can I print out the updated grid the way I have implemented this? If I were to put the display grid for loop in a separate function I would need to call the 2d array as a parameter which I'm sure you cannot do.

Here is what I have:

void generateGrid(int diff){
        srand(time(NULL));
        int arr[maximum][maximum];
            for (int i=0;i<diff;i++)
        {
            for (int j=0;j<diff;j++)
            {
                arr[i][j] = rand() % 9 + 1;
            }
        }
        cout<<"\n\tPuzzle\n\t";
            for(int i=0;i<diff;i++)
            {
                cout<<i<<" ";
            }
                cout<<"\n\n";
            for(int i=0;i<diff;i++)
            {
                cout<<i<<"\t";
                for(int j=0;j<diff;j++)
                {
                    cout<<arr[i][j]<<" ";
                }
                    cout<<"\n";
            }
       int x, y;
        cout<<"\nEnter x value: ";
        cin>>x;
        cout<<"Enter y value: ";
        cin>>y;
        arr[x][y] = 0;
    }

Diff refers to the puzzle size (difficulty)

Elsewhere:

int easy = 5;
int medium = 8;
int hard = 10;
int maximum = 10;

Solution 1

Standard C++ does not support setting individual characters at positions in the console without re-printing. This is OS-specific, and there are comments that address this.

Otherwise, the correct solution is to encapsulate your game board logic into a class. We can use a nested std::vector to handle a dynamically-sized board, and provide functions for getting and setting cells. A separate Print function allows us to print the board to the console as often as we'd like.

class Grid
{
    public:
    Grid(int size) : myGrid(size, std::vector<int>(size, 0)) // initialize grid to be correctly sized and all zeros
    {
       Randomize();
    }

    void Randomize()
    {
        for (size_t i=0;i<myGrid.size();i++)
        {
            for (size_t j=0;j<myGrid[i].size();j++)
            {
                myGrid[i][j] = rand() % 9 + 1;
            }
        }
    }

    void Print(std::ostream& out) const
    {
        out<<"\n\tPuzzle\n\t";
        for(size_t i=0;i<myGrid.size();i++)
        {
           out<<i<<" ";
        }
        out << "\n\n";
        for(size_t i=0;i<myGrid.size();i++)
        {
            out<<i<<"\t";
            for(size_t j=0;j<myGrid[i].size();j++)
            {
                out<<myGrid[i][j]<<" ";
            }
            out<<"\n";
        }
    }

    int GetValue(size_t row, size_t col) const
    {
        // use wraparound for too-large values
        // alternatively you could throw if row and/or col are too large
        return myGrid[row % myGrid.size()][col % myGrid.size()];
    }

    void SetValue(size_t row, size_t col, int val)
    {
        myGrid[row % myGrid.size()][col % myGrid.size()] = val;
    }

    private:
    std::vector<std::vector<int>> myGrid;         
};

Now you can write your main like so:

int main()
{
    srand(time(NULL));
    Grid board(10);
    size_t xValue = 0;
    size_t yValue = 0;

    // game loop. You could even abstract this behavior into another class
    while(true)
    {
        board.Print(std::cout);
        std::cout<<"\nEnter x value: ";
        if (!std::cin) // check for no input
            break;
        std::cin>>xValue;
        if (!std::cin) // check for end of input
           break;
        std::cout<<"Enter y value: ";
        std::cin>>yValue;
        if (!std::cin)
            break;
        board.SetValue(xValue, yValue, 0);

        // other game logic...
    }

    // print board one last time before exit
    std::cout << "Game over. Final board: \n";
    board.Print(std::cout);
}

Live Demo

Solution 2

If your console supports ANSI escape codes, you can go up multiple lines and re-print them, e. g. like this:

printf("hello\n");
printf("\x1b[A");  // you can add the number of lines: "\x1b[7A"
printf("hola \n"); // add sufficient spaces to overwrite previous output!

This works under most linux shells, Windows, however, does not support it until Win10.

Comments

[GordanAndrews]

That's a very interesting way to look at it. Are there ways to manipulate the board states and properties? Such as saving a particular board state and restarting that saved state. I'm also curious it it's possible to actually sort the numbers within the puzzle in ascending order per row.

[AndyG]

@GordanAndrews yes for sure. It just takes a little learning. For saving, you could write to a file stream. And of course you can sort each sub vector, either manually or with library calls

[Aconcagua]

To be noted: Windows specific solution (corresponding linux command is clear – on some terminals previous output is just moved out of sight, though, and can still be accessed by scrolling...).