C++ Program to Find if an Array is an Identity Matrix

In this tutorial, we will learn and write a C++ program to check whether a given matrix is an identity matrix or not. To understand the coding, you should have knowledge of the following topics in C++ programming:

• C++ Arrays
• C++ loops

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Identity Matrix:

A square matrix is said to be an identity matrix if each entry on its diagonal is equal to 1 and the rest are 0. Example:

Matrix of dimension 3 by 3:
1 0 0
0 1 0
0 0 1

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Explanation: The program takes user input for the number of rows and columns of a matrix. The values are of each element are also taken from the user.

Before entering the elements of the matrix, the program also checks for the matrix to be a square matrix. If it is a square matrix then the execution control moves to the next line but if not then the program is exited.

The program checks the diagonals matrix for 1 and the rest for 0. If the conditions are found to be true then the entered matrix is identity matrix else not.

Now let us go through a program for Identity Matrix in C++.

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C++ Program to Find if an Array is an Identity Matrix

#include <iostream>
using namespace std;

int main()
{
  int i, j, row, col, arr[10][10], flag = 0;

  cout << "Enter the number of rows: ";
  cin >> row;
  cout << "Enter the number of column: ";
  cin >> col;

  //Checking for square matrix
  if (row != col)
  {
    cout << "\nMatrix is not a square matrix. Try Again!";
    exit(0);
  }

  cout << "\nEnter the elements of matrix:\n";
  for (i = 0; i < row; i++)
    for (j = 0; j < col; j++)
      cin >> arr[i][j];

  //Checking for diagonals and rest
  for (i = 0; i < row; i++)
  {
    for (j = 0; j < col; j++)
    {
      if ((arr[i][j] != 1) && (arr[j][i] != 0))
      {
        flag = 1;
        break;
      }
    }
  }

  //Display accordingly
  if (flag == 0)
    cout << "\nThe entered matirix is an identity matrix.\n";
  else
    cout << "\nThe entered matirix is NOT an identity matrix.";

  //Display the matrix
  for (i = 0; i < row; i++)
  {
    for (j = 0; j < col; j++)
      cout << arr[i][j] << " ";
    cout << "\n";
  }

  return 0;
}

Output:

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