// Program to decide whether the matrix is a 
// lower triangular matrix. 
/* A square matrix where all elements above 
the main diagonal are zero is called a lower 
triangular matrix. Eg.: 
  c0 c1 c2 
r0 2  0  0 
r1 1  5  0
r2 1 -1 -2
*/

#include <stdio.h>

#define MAX_ROW 3
#define MAX_COL 3

int is_lower_tri(int array[MAX_ROW][MAX_COL]);

int main(void) {
    int array[MAX_ROW][MAX_COL] = {{2, 0, 0}, {1, 5, 0}, {1, -1, -2}};
    if (is_lower_tri(array)) {
        printf("The matrix is a lower triangular matrix\n");
    } else {
        printf("The matrix is NOT a lower triangilar matrix\n");
    }
    return 0;
}

int is_lower_tri(int array[MAX_ROW][MAX_COL]) {
    int is_lower = 1 ;

    for(int i = 0; i < MAX_ROW; i++) {
        for(int j = 0; j < MAX_COL; j++) {
            if(j > i && array[i][j] != 0) {
                is_lower = 0;
            }
        }
    }
    return is_lower;
}