Question

How to check if a matrix is an identity matrix (ones on the main diagonal and zeros elsewhere) in C++

Answer 1

#include <iostream>

int main()
{   
    int matrix[3][3] = {{1, 0, 0},
                        {0, 1, 0},
                        {0, 0, 1}};
  
    size_t rows = sizeof matrix/sizeof matrix[0];
    size_t cols = (sizeof matrix/sizeof matrix[0][0])/rows;
 
    int identity = 1;
    for (int i = 0; i < rows; i++) {
		for (int j = 0; j < cols; j++) {
			if (i == j && matrix[i][j] != 1) {
				identity = 0;
				break;
			}
			else {
			    if (i != j && matrix[i][j] != 0) {
				    identity = 0;
				    break;
			    }
			}
		}
	}

 
	if (identity) {
		std::cout << "Identity matrix";
	}
	else {
		std::cout << "NOT identity matrix";
	}
     
    return 0;
}
 
 
 
   
/*
run:
 
Identity matrix
 
*/

 

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