C Program to find Lower Triangle Matrix

A Lower triangle Matrix is a square matrix where elements above the main diagonal are zeros. In this article, we will show you, How to write a C Program to find Lower Triangle Matrix with example.

C Program to find Lower Triangle Matrix Example

This program allows the user to enter the number of rows and columns of a Matrix. Next, we are going to find the Lower triangle of this matrix using For Loop.

/* C Program to find Lower Triangle Matrix */
 
#include<stdio.h>
 
int main()
{
 	int i, j, rows, columns, a[10][10];
  
 	printf("\n Please Enter Number of rows and columns  :  ");
 	scanf("%d %d", &i, &j);
 
 	printf("\n Please Enter the Matrix Elements \n");
 	for(rows = 0; rows < i; rows++)
  	{
   		for(columns = 0;columns < j;columns++)
    	{
      		scanf("%d", &a[rows][columns]);
    	}
  	}
     
 	for(rows = 0; rows < i; rows++)
  	{
  		printf("\n");
   		for(columns = 0; columns < j; columns++)
    	{
    		if(rows >= columns)
    		{
    			printf("%d ", a[rows][columns]);
			}
			else
			{
				printf("0  ");
			}
   	 	}
  	}
  	
 	return 0;
}

OUTPUT

ANALYSIS
In this Program, We declared single Two dimensional arrays Multiplication of size of 10 * 10.

Below statements asks the User to enter the Matrix size (Number of rows and columns. For instance 2 Rows, 2 Columns = a[2][2] )

printf("\n Please Enter Number of rows and columns  :  ");
scanf("%d %d", &i, &j);

Next, we used for loop to iterate each and every cell present in a[2][2] matrix. Conditions inside the for loops ((rows < i) and (columns < j)) will ensure the compiler, not to exceed the matrix limit. Otherwise the matrix will overflow

scanf statement inside the for loop will store the user entered values in every individual array element such as a[0][0], a[0][1], …..

for(rows = 0; rows < i; rows++).
{
  for(columns = 0; columns < j; columns++)
   {
     scanf("%d", &a[rows][columns]);
   }
}

In the next line, We have one more for loop to find Lower Triangle of a Matrix

for(rows = 0; rows < i; rows++)
{
	printf("\n");
	for(columns = 0; columns < j; columns++)
    	{
    		if(rows >= columns)
    		{
    			printf("%d ", a[rows][columns]);
		}
		else
		{
			printf("0  ");
		}
 	}
}

User inserted values are: a[2][2] = {{10, 20}, { 30, 40}}

Row First Iteration: for(rows = 0; rows < 2; 0++)
The condition (0 < 2) is True.

Column First Iteration: for(columns = 0; 0 < 2; 0++)
The condition (columns < 2) is True. So, it will start executing the statements inside the loop
if(rows >= columns) => if(0 >= 0)
This condition is True. So, it will print a[0][0] = 10

Column Second Iteration: for(columns = 1; 1 < 2; 1++)
The condition (columns < 2) is True.
if(rows >= columns)=> if(0 >= 1)
This condition is False. So, it will print 0

Column Third Iteration: for(columns = 2; 2 < 2; 2++)
The condition (columns < 2) is False. So it will exit from the loop.
Next, rows value will be incremented to 1.

Row Second Iteration: for(rows = 1; rows < 2; 1++)
The condition (1 < 2) is True.

Column First Iteration: for(columns = 0; 0 < 2; 0++)
The condition (columns < 2) is True. So, it will start executing the statements inside the loop
if(rows >= columns) => if(1 >= 0)
This condition is False. So, it will print a[1][0] = 30

Column Second Iteration: for(columns = 1; 1 < 2; 1++)
The condition (columns < 2) is True.
if(rows >= columns) => if(1 >= 1)
This condition is True. So, it will print a[1][1] = 40

Column Third Iteration: for(columns = 2; 2 < 2; 2++)
The condition (columns < 2) is False. So it will exit from the loop.

Next, rows value will be incremented to 1. After the increment the condition inside the first for loop (rows < 2) will fail. So it will exit from the loop.

Let me try the same with 3 * 3 matrix

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