Emulating a 2d array using 1d array (original) (raw)

Last Updated : 11 Sep, 2023

How to convert a 2-d array of size (m x n) into 1-d array and how to store the element at position [i, j] of 2-d array in 1-d array? Clearly, the size of 1-d array is the number of elements in 2-d array i.e.

m x n). If the elements in the 2-d array are stored in row-major order. Then, the element at index [i, j] in 2-d array will be stored in 1-d array at index k as:

k = j + (i * total_no_of_columns_in_matrix)

If the elements in the 2-d array are stored in column-major order, the value of index k will be

k = i + (j * total_no_of_rows_in_matrix)

Examples :

Given 2-d array:

// array is formed in row-major order __________________________ | | |1(0,0) 2(0,1) 3(0,2)| | | |4(1,0) 5(1,1) 6(1,2)| |__________________________|

// The elements in parenthesis represents the // index of the particular element in 2-d array.

Index of element at (0,1) in 1-d array will be: k(0,1) = 1 + 0 * 3 = 1

Index of element at (1,1) in 1-d array will be: k(1,1) = 1 + 1 * 3 = 4

Implementation:

C++ `

// C++ program to emulate 2-d array using // 1-d array #include<stdio.h> #define n 3 #define m 3 #define max_size 100 int main() {

// Initialising a 2-d array
int grid[n][m] = {{1, 2, 3},
                  {4, 5, 6},
                  {7, 8, 9}};

// storing elements in 1-d array
int i, j, k = 0;
int array[max_size];
for (i=0; i<n; i++)
{
    for (j=0; j<m; j++)
    {
        k = i*m + j;
        array[k] = grid[i][j];
        k++;
    }
}

// displaying elements in 1-d array
for (i=0; i<n; i++)
{
    for (j=0; j<m; j++)
        printf("%d ", *(array + i*m + j));
    printf("\n");
}

return 0;

}

Java

// Java program to emulate 2-d array using // 1-d array

class GFG { // Driver program public static void main(String arg[]) { // Declaring number of rows and columns int n = 3, m = 3; int array[]=new int[100];

    // Initialising a 2-d array
    int grid[][] = {{1, 2, 3},
                    {4, 5, 6},
                    {7, 8, 9}};

    // storing elements in 1-d array
    int i, j, k = 0;
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
        {
            k = i * m + j;
            array[k] = grid[i][j];
            k++;
        }
    }

    // displaying elements in 1-d array
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
            System.out.print((array[i * m + j])+" ");
        System.out.print("\n");
    }

}

}

// This code is contributed by Anant Agarwal.

Python3

Python program to emulate 2-d

array using 1-d array

Declaring number of rows and columns

n = 3; m = 3

array = [0 for i in range(100)]

Initialising a 2-d array

grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];

storing elements in 1-d array

k = 0

for i in range(n): for j in range(m):

    k = i*m + j
    array[k] = grid[i][j]
    k += 1

displaying elements in 1-d array

for i in range(n): for j in range(m): print((array[i*m + j]), " ", end = "") print()

This code is contributed by Anant Agarwal.

C#

// C# program to emulate 2-d array using // 1-d array using System;

class GFG { // Driver program public static void Main() { // Declaring number of rows and columns int n = 3, m = 3; int []array=new int[100];

    // Initialising a 2-d array
    int [,]grid = {{1, 2, 3},
                    {4, 5, 6},
                    {7, 8, 9}};

    // storing elements in 1-d array
    int i, j, k = 0;
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
        {
            k = i * m + j;
            array[k] = grid[i, j];
            k++;
        }
    }

    // displaying elements in 1-d array
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
            Console.Write((array[i * m + j])+" ");
        Console.Write("\n");
    }

}

}

// This code is contributed by nitin mittal

JavaScript

Time Complexity: O(n*m)
Auxiliary Space: O(n*m)