C++ Program For Addition of Two Matrices

Given two N x M matrices. Find a N x M matrix as the sum of given matrices each value at the sum of values of corresponding elements of the given two matrices. 

Approach: Below is the idea to solve the problem.

Iterate over every cell of matrix (i, j), add the corresponding values of the two matrices and store in a single matrix i.e. the resultant matrix.

Follow the below steps to Implement the idea:

• Initialize a resultant matrix res[N][M].
• Run a for loop for counter i as each row and in each iteration:
  • Run a for loop for counter j as each column and in each iteration:
    • Add values of the two matrices for index i, j and store in res[i][j].
• Return res.

Below is the Implementation of the above approach:

C++

// C++ program for addition
// of two matrices
#include <bits/stdc++.h>
using namespace std;
#define N 4

// This function adds A[][] and B[][],
// and stores the result in C[][]
void add(int A[][N], int B[][N],
         int C[][N])
{
    int i, j;
    for (i = 0; i < N; i++)
        for (j = 0; j < N; j++)
            C[i][j] = A[i][j] + B[i][j];
}

// Driver code
int main()
{
    int A[N][N] = {{1, 1, 1, 1},
                   {2, 2, 2, 2},
                   {3, 3, 3, 3},
                   {4, 4, 4, 4}};

    int B[N][N] = {{1, 1, 1, 1},
                   {2, 2, 2, 2},
                   {3, 3, 3, 3},
                   {4, 4, 4, 4}};

    // To store the result
    int C[N][N];
    int i, j;
    add(A, B, C);

    cout << "Result matrix is " <<
             endl;
    for (i = 0; i < N; i++)
    {
        for (j = 0; j < N; j++)
        cout << C[i][j] << " ";
        cout << endl;
    }

    return 0;
}

Output:

Result matrix is
2 2 2 2
4 4 4 4
6 6 6 6
8 8 8 8

The program can be extended for rectangular matrices. The following post can be useful for extending this program: How to pass a 2D array as a parameter in C?
The time complexity of the above program is O(n²). 

The auxiliary space of the above problem is O(n²)