Dynamical Two Dimension Array According to Input

dynamical two dimension array according to input

Boost implements matrices (supporting mathematical operations) in its uBLAS library, and provides usage syntax like the following.

#include <boost/numeric/ublas/matrix.hpp>

int main(int argc, char* argv[])
{
    unsigned int N = atoi(argv[1]);
    boost::matrix<int> myMatrix(N, N);

    for (unsigned i = 0; i < myMatrix.size1 (); ++i)
        for (unsigned j = 0; j < myMatrix.size2 (); ++j)
            myMatrix(i, j) = 3 * i + j;

    return 0;
}

How to take inputs for 2 Dimensional dynamic array in Java?

You have 3 issues with your code:

1. You never initialize the inner arrays. Do it with arr[z] = new char[s.length()];.
2. The way you define arrOfStr. You split the string by the blank sub-string. Instead just use s use charAt like this:
   arr[z][y] = s.charAt(y);
3. As the comments suggested, there is the issue with nextInt that does not take into account the \n (enter) char.
   So use int no=Integer.parseInt(in.nextLine());, instead of using nextInt.

The final code should look like this:

for(z=0 ; z<no ; z++)
{
    String s = in.nextLine(); 
    arr[z] = new char[s.length()];
    for( y =0 ; y<s.length() ; y++)
    {
        arr[z][y]=s.charAt(y);
    }
}   

Creating N-dimensional dynamical array based on user's input?

>>> rows = 486
>>> columns = 5
>>> A = [[None] * columns for x in xrange(rows)]
>>> len(A)
486
>>> len(A[0])
5

Dynamically Allocated input, and output 2-D Arrays in C++

I solved it:

#include <iostream>
//#include <vector>

using namespace std;

int main() {
int row, col;
cout << "Please enter the rows size: " << endl;
cin >> row;
cout << "Please enter the column size: " << endl;
cin >> col;

cout << "Please enter the numbers you want to put into a 2D array (it should 
look like a matrix graph)." << endl;
cout << "Press enter after each number you input: " << endl;

int** map = new int*[row];
for (int i = 0; i < row; ++i)
    map[i] = new int[col];

for (int i = 0; i < row; i++) {
    for (int j = 0; j < col; j++) {
        cin >> map[i][j];
    }

}

cout << endl;
//Print
for (int i = 0; i < row; i++) {
    for (int j = 0; j < col; j++) {
        cout << map[i][j] << " ";
    }
    cout << endl;

}
cout << endl;


// DON'T FORGET TO FREE
for (int i = 0; i < row; ++i) {
    delete[] map[i];
}
delete[] map;
system("pause");
return 0;
}

2D Dynamic Array Based on User Input

A better way to do your current program, using std::vector, could be like this:

#include <iostream>
#include <vector>
#include <fstream>

int main()
{
    std::ifstream dataFile("data.txt");

    // Get the number of "rooms"
    unsigned roomCount;
    if (!(dataFile >> roomCount))
    {
        // TODO: Handle error
    }

    // Create the vector to contain the rooms
    std::vector<std::vector<int>> rooms(roomCount);

    for (unsigned currentRoom = 0; currentRoom < roomCount; ++currentRoom)
    {
        unsigned personCount;
        if (dataFile >> personCount)
        {
            rooms[currentRoom].resize(personCount);
        }
        else
        {
            // TODO: Handle error
        }
    }

    // Don't need the file anymore
    dataFile.close();

    // Print the data
    std::cout << "Number of rooms: " << rooms.size() << '\n';
    for (unsigned currentRoom = 0; currentRoom < rooms.size(); ++currentRoom)
    {
        std::cout << "Room #" << currentRoom + 1 << ": " << rooms[currentRoom].size() << " persons\n";
    }
}

As you can see, it's now possible to get the "sizes" of the data after you're done with the reading from the file.

Reading two dimensional array with dynamic size of integers and output it vertically

You can do it by taking the input line by line, and then extracting the numbers delimited by space using strtok. See the code live here

#include <stdio.h> 
#include <stdlib.h>
#include <string.h>

void input_matrix(int matrix[][100], int *rows, int *cols)
{
    char *buffer;
    size_t buffer_size = 200;

    int row = 0;
    int col = 0;
    int ret;

    buffer = (char *)malloc(sizeof(char) * buffer_size);

    while((ret = getline(&buffer, &buffer_size, stdin)) > 0) {
            char *split = NULL;
            //printf("ret: %d\n", ret);
            split = strtok(buffer, " ");

            col = 0;

            while (split) {
                matrix[row][col] = strtol(split, NULL, 10);
                col++;

                split = strtok(NULL, " ");
            }

            row++;
    }
    free(buffer);

    *rows = row;
    *cols = col;
}

void print_matrix(int matrix[][100], int rows, int cols)
{
    printf("Printing matrix: \n");

    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
}

void print_transpose(int matrix[][100], int rows, int cols)
{
    printf("Printing transpose: \n");

    for (int j = 0; j < cols; j++) {
        for (int i = 0; i < rows; i++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
}

int main() 
{
    int m_input[100][100]; 

    int rows;
    int cols;

    input_matrix(m_input, &rows, &cols);

    printf("Input row: %d, col: %d\n", rows, cols);


    print_matrix(m_input, rows, cols);


    print_transpose(m_input, rows, cols); 

    return 0; 
} 

Changing the size of a two-dimensional array based on user input

Assuming you know how to POST the data from the html form back to your server, the php code which processes the request could look something like the following. It seems your question comes down to how to code a dynamically sized 2-dimensional array (matrix).

create a nested for loop. The inner for loop builds each row ( $this_row ) by appending items to it: $this_row[] = rand($min, $max);, then each new row is appended to the $matrix array.

Keep in mind the rand function and $min and $max variables are not defined in the following example. You'll need to define them.

<?php

    $num_cols = filter_input(INPUT_POST, 'columns', FILTER_VALIDATE_INT);
    $num_rows = filter_input(INPUT_POST, 'rows', FILTER_VALIDATE_INT);

    $matrix = array();

    for ( $j = 0; $j < $num_rows; $j ++ ) {
        $this_row = array()
        for ( $k = 0; $k < $num_cols; $k ++ ) {
            $this_row[] = rand($min, $max);
        }
        $matrix[] = $this_row;
    }

    //now you have your matrix

?>

Is it possible to dynamically build a multi-dimensional array in Java?

It is actually possible to do in java. (I'm a bit surprised I must say.)

Disclaimer; I never ever want to see this code anywhere else than as an answer to this question. I strongly encourage you to use Lists.

import java.lang.reflect.Array;
import java.util.*;

public class Test {

    public static int[] tail(int[] arr) {
        return Arrays.copyOfRange(arr, 1, arr.length);
    }

    public static void setValue(Object array, String value, int... indecies) {
        if (indecies.length == 1)
            ((String[]) array)[indecies[0]] = value;
        else
            setValue(Array.get(array, indecies[0]), value, tail(indecies));
    }

    public static void fillWithSomeValues(Object array, String v, int... sizes) {
        for (int i = 0; i < sizes[0]; i++)
            if (sizes.length == 1)
                ((String[]) array)[i] = v + i;
            else
                fillWithSomeValues(Array.get(array, i), v + i, tail(sizes));
    }

    public static void main(String[] args) {

        // Randomly choose number of dimensions (1, 2 or 3) at runtime.
        Random r = new Random();
        int dims = 1 + r.nextInt(3);

        // Randomly choose array lengths (1, 2 or 3) at runtime.
        int[] sizes = new int[dims];
        for (int i = 0; i < sizes.length; i++)
            sizes[i] = 1 + r.nextInt(3);

        // Create array
        System.out.println("Creating array with dimensions / sizes: " +
                Arrays.toString(sizes).replaceAll(", ", "]["));
        Object multiDimArray = Array.newInstance(String.class, sizes);

        // Fill with some 
        fillWithSomeValues(multiDimArray, "pos ", sizes);

        System.out.println(Arrays.deepToString((Object[]) multiDimArray));


    }
}

Example Output:

Creating array with dimensions / sizes: [2][3][2]
[[[pos 000, pos 001], [pos 010, pos 011], [pos 020, pos 021]],
 [[pos 100, pos 101], [pos 110, pos 111], [pos 120, pos 121]]]

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