c print formatted 2D array-CodePudding

I am trying to print a 2d matrix in c . I have a 2D array of integers. The output looks like this:

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 
0 0 0 0 0 0 0 0 0 0 60 60 60 60 60 60 60 60 60 60 100 100 100 100 100 100 100 100 100 100 160

My code simply does 2 loops and adds an space after each number (and a newline after every row). Is there an easy way to print nicely formatted matrix in cpp. Something that would be more readable like so:

0 0 0 0 0 0 0  0  0   0   0 
0 0 0 0 0 0 60 60 60  60  60
0 0 0 0 0 0 60 60 100 100 160

Code:

for(int i = 0; i <= n ; i  ){
    for(int w = 0; w <= W ; w  ){
        std:cout<<some_array[i][w]<<"   ";
    }
    std::cout << std::endl;
}

CodePudding user response：

This overload of the output stream operator will do the formatting for you. And then the code where you do the output will look quite clean.

#include <iostream>

template<typename type_t, std::size_t rows_v, std::size_t cols_v>
std::ostream& operator<<(std::ostream& os, type_t (&arr)[rows_v][cols_v])
{
    // loop over the rows
    for (const auto& row : arr)
    {
        // to print a comma between values
        bool comma{ false };

        // loop over the values in the row
        for (const auto& value : row)
        {
            if (comma) os << ", ";
            os << value;
            comma = true;
        }
        os << "\n";
    }

    return os;
}

int main()
{
    int arr[2][3]{{0,1,2},{4,5,6}};
    std::cout << arr << "\n";
    return 0;
}

CodePudding user response：

Quick code that does this, could be made better:

#include <iostream>
#include <string>

int main()
{
    int maxwidth = 0;
    int sz;
    std::string s;

    int K[3][31] = {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
                {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60},
                {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 160}};

    for (int i = 0; i < 3; i  )
    {
        for (int w = 0; w < 31; w  )
        {
            s = std::to_string(K[i][w]);
            sz = s.size();
            maxwidth = std::max(maxwidth, sz);
        }
    }

    maxwidth  ; // we need to print 1 extra space than maxwidth

    for (int i = 0; i < 3; i  )
    {
        for (int w = 0; w < 31; w  )
        {
            std::cout << K[i][w];
            s = std::to_string(K[i][w]);
            sz = (maxwidth - s.size());
            while (sz--)
                std::cout << " ";
        }
        std::cout << std::endl;
    }
    return 0;
}

Output:

0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
0   0   0   0   0   0   0   0   0   0   60  60  60  60  60  60  60  60  60  60  60  60  60  60  60  60  60  60  60  60  60  
0   0   0   0   0   0   0   0   0   0   60  60  60  60  60  60  60  60  60  60  100 100 100 100 100 100 100 100 100 100 160