Two-dimensional arrays

[pushkin]

Hi. so i have a two dimensional array , who's parameters are decided by the user . Hence i cannot initialize it . Now i want to take input for the first the row and then check some condition and then move on and take input for the next row.
Please Help mee...

[condor]

Take a look here:

http://www.cplusplus.com/doc/tutorial/dynamic/

[pushkin]

Yes, thanks. but how do i take input for only the first row and check something and then go to the next row . considering that its a two dimensional array

[JLBorges]

#include <iostream>
#include <vector>

int main()
{
    std::size_t rows, cols ;
    std::cout << "number of rows? " ;
    std::cin >> rows ;
    std::cout << "number of cols? " ;
    std::cin >> cols ;

    std::vector< std::vector<int> > array_2d ;

    // read in the values for the first row
    std::vector<int> row ;
    std::cout << "please enter " << cols << " values for the first row: " ;
    for( std::size_t i = 0 ; i < cols ; ++i )
    {
        int value ;
        std::cin >> value ;
        row.push_back(value) ;
    }

    // TODO: check some cindition on the first rwo

    // add the row to array_2d
    array_2d.push_back(row) ;

    // no repeat for the remaining row-1 rows
    for( std::size_t i = 1 ; i < rows ; ++i )
    {
        std::cout << "please enter " << cols << " values for row #" << i << ": " ;
        for( std::size_t j = 0 ; j < cols ; ++j )
        {
            int value ;
            std::cin >> value ;
            row.push_back(value) ;
        }

        // add this row to array_2d
        array_2d.push_back(row) ;
    }
}

[condor]

@pushkin

In my opinion you must begin with the necessary declarations and then enter the elements of the matrix. Then make your checks. Here's an attempt for an 2-dimension array:

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#include <iostream> #include <iomanip> using namespace std; int main() { int row, col; cout << "Enter how many rows: "; cin >> row; cout << "Enter how many columns: "; cin >> col; // dynamic memory allocation: // you can use any type instead of int int **myArray = new int *[row]; for(int i = 0; i < row; ++i) myArray[i] = new int[col]; cout << "\nEnter the elements of the matrix\n\n"; for (int i=0; i < row; i++) { for (int j=0; j < col; j++) { cout << "Row " << i + 1 << " Col " << j + 1 << ": "; cin >> myArray[i][j]; } cout <<'\n'; } cout << "Check: \n\n"; for(int i = 0; i < row; ++i) { for(int j = 0; j < col; ++j) cout << setw(8) << myArray[i][j]; cout << '\n'; } //----- your code ---- //free the allocated memory for(int i = 0 ; i < row ; ++i ) delete [] myArray[i] ; delete [] myArray ; return 0; }

Enter how many rows: 3 Enter how many columns: 4 Enter the elements of the matrix Row 1 Col 1: 1 Row 1 Col 2: 2 Row 1 Col 3: 3 Row 1 Col 4: 4 Row 2 Col 1: 5 Row 2 Col 2: 6 Row 2 Col 3: 7 Row 2 Col 4: 8 Row 3 Col 1: 9 Row 3 Col 2: 10 Row 3 Col 3: 11 Row 3 Col 4: 12 Check: 1 2 3 4 5 6 7 8 9 10 11 12

[pushkin]

@condor
Thanks . But it didn't help that much .
My code is very much similar to the one you wrote above ..
referring to your code.
the only difference is that i have to print the two dimensional array after the user provides the row 1 col 1-4 1
Wondering if you could help me with that .
thanks:)

[condor]

OK, see the next code modified how it seems that may interest you, I hope.

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#include <iostream> #include <iomanip> using namespace std; template<typename T> void printArray(int l, int m, int n, T arg) { for(int i = l; i < m; ++i) { for(int j = 0; j < n; ++j) cout << setw(8) << arg[i][j]; cout << '\n'; } } int main() { int row, col; cout << "Enter how many rows: "; cin >> row; cout << "Enter how many columns: "; cin >> col; // dynamic memory allocation: // you can use any type instead of int int **myArray = new int *[row]; for(int i = 0; i < row; ++i) myArray[i] = new int[col]; cout << "\nEnter the elements of the matrix\n\n"; for (int i=0; i < row; i++) { cout << "Row " << i + 1 << '\n'; for (int j=0; j < col; j++) { cout << " Col " << j + 1 << ": "; cin >> myArray[i][j]; } // your check code // ... // for example print out the actual array: cout << "\nCheck row " << i + 1 << " : \n"; printArray(i, i + 1, col, myArray); cout << "Plus the result(s) of your check code...\n"; // end of the check code and continue with // the next input line cout <<'\n'; } cout << "Entered matrix: \n"; printArray(0, row, col, myArray); //----- the rest of your code ---- //free the allocated memory for(int i = 0 ; i < row ; ++i ) delete [] myArray[i] ; delete [] myArray ; return 0; }

Enter how many rows: 3 Enter how many columns: 4 Enter the elements of the matrix Row 1 Col 1: 1 Col 2: 2 Col 3: 3 Col 4: 4 Check row 1 : 1 2 3 4 Plus the result(s) of your check code... Row 2 Col 1: 5 Col 2: 6 Col 3: 7 Col 4: 8 Check row 2 : 5 6 7 8 Plus the result(s) of your check code... Row 3 Col 1: 9 Col 2: 10 Col 3: 11 Col 4: 12 Check row 3 : 9 10 11 12 Plus the result(s) of your check code... Entered matrix: 1 2 3 4 5 6 7 8 9 10 11 12