Print lower triangular matrix pattern from given array in C Program.

Given with the matrix of n x n the task is to print that matrix of n x n in lower triangular pattern.

Lower triangular matrix is a matrix which has elements below the principle diagonal including the principle diagonal elements and rest elements as zero.

Let’s understand this with help of a diagram −

Above the elements in green are the elements below the principle diagonal and the red elements are the elements above the principle diagonal which are set as zero.

Example

Input: matrix[3][3] = {
   { 1, 2, 3 },
   { 4, 5, 6 },
   { 7, 8, 9 } }
Output:
   1 0 0
   4 5 0
   7 8 9

Algorithm

int lower_mat(int mat[n][m])
START
STEP 1: DECLARE I AND j
STEP 2 : LOOP FOR i = 0 AND i < n AND i++
   LOOP FOR j = 0 AND j < m AND j++
      IF i < j THEN,
         PRINT "0\t"
      ELSE
         PRINT mat[i][j]
      END IF
   END FOR
   PRINT newline
END FOR
STOP

Example

#include <stdio.h>
#define n 3
#define m 3
int lower_mat(int mat[n][m]){
   int i, j;
   for ( i = 0; i < n; i++){
      for ( j = 0; j < m; j++){
         if( i < j )
            printf("0\t");
         else
            printf("%d\t", mat[i][j]);
      }
      printf("\n");
   }
}
int main(int argc, char const *argv[]){
   int mat[n][m] = {
      {1, 2, 3},
      {4, 5, 6},
      {7, 8, 9}
   };
   lower_mat(mat);
   return 0;
}

Output

If we run above program then it will generate following output −

1 0 0
4 5 0
7 8 9