C++ Program to Print Lower Triangle of a Matrix

Write a C++ Program to Print Lower Triangle of a Matrix with an example. The following image shows you the lower triangle of a matrix.

In this C++ matrix lower triangle example, we used nested for loops to iterate lowerTriMatrix matrix rows and columns. Within that loop, we used C++ If Else statement (if(rows >= columns)) to check whether the row value is greater than or equal to the column value. If True, print the matrix item at that position; otherwise, print 0 in that position.

#include<iostream>
using namespace std;

int main()
{
	int i, j, rows, columns;
	
	cout << "\nPlease Enter Matrix rows and Columns to find Lower Triangle =  ";
	cin >> i >> j;
	
	int lowerTriMatrix[i][j];
	
	cout << "\nPlease Enter the Matrix Items\n";
	for(rows = 0; rows < i; rows++)	{
		for(columns = 0; columns < i; columns++) {
			cin >> lowerTriMatrix[rows][columns];
		}		
	}

 	cout << "\nThe Result of the Lower Triangle Matrix is :\n";
 	for(rows = 0; rows < i; rows++)
  	{
  		cout << "\n";
   		for(columns = 0; columns < j; columns++)
    	{
    		if(rows >= columns)
    		{
    			cout << lowerTriMatrix[rows][columns] << " ";
			}
			else
			{
				cout << "0 ";
			}
   	 	}
  	}	

 	return 0;
}

In this C++ Matrix Lower Triangle example, we used some extra cout statements to show you the iteration-wise row, column values, and lowerTriMatrix[rows][columns] value.

#include<iostream>
using namespace std;

int main()
{
	int i, j, rows, columns;
	
	cout << "\nPlease Enter Matrix rows and Columns to find Lower Triangle =  ";
	cin >> i >> j;
	
	int lowerTriMatrix[i][j];
	
	cout << "\nPlease Enter the Matrix Items\n";
	for(rows = 0; rows < i; rows++)	{
		for(columns = 0; columns < i; columns++) {
			cin >> lowerTriMatrix[rows][columns];
		}		
	}

 	cout << "\nThe Result of the Lower Triangle Matrix is :\n";
 	for(rows = 0; rows < i; rows++)
  	{
  		cout << "\n";
   		cout << "\nRow Iteration = " << rows + 1 << ", Row Number = " << rows;
   		for(columns = 0; columns < j; columns++)
    	{
    		cout << "\nColumn Iteration = " << columns + 1 << ", Column Number = " << 
			  	columns << ", and Row Number = " << rows;
			cout << "\nThe result of (rows >= columns) = " << (rows >= columns) << 
				" and lowerTriMatrix[" << rows << "][" << columns << "] = " << lowerTriMatrix[rows][columns] << endl;
    		if(rows >= columns)
    		{
    			cout << lowerTriMatrix[rows][columns] << " ";
			}
			else
			{
				cout << "0 ";
			}
   	 	}
  	}	

 	return 0;
}

Please Enter Matrix rows and Columns to find Lower Triangle =  3 3

Please Enter the Matrix Items
1 2 3
4 5 6
7 8 9

The Result of the Lower Triangle Matrix is :


Row Iteration = 1, Row Number = 0
Column Iteration = 1, Column Number = 0, and Row Number = 0
The result of (rows >= columns) = 1 and lowerTriMatrix[0][0] = 1
1 
Column Iteration = 2, Column Number = 1, and Row Number = 0
The result of (rows >= columns) = 0 and lowerTriMatrix[0][1] = 2
0 
Column Iteration = 3, Column Number = 2, and Row Number = 0
The result of (rows >= columns) = 0 and lowerTriMatrix[0][2] = 3
0 

Row Iteration = 2, Row Number = 1
Column Iteration = 1, Column Number = 0, and Row Number = 1
The result of (rows >= columns) = 1 and lowerTriMatrix[1][0] = 4
4 
Column Iteration = 2, Column Number = 1, and Row Number = 1
The result of (rows >= columns) = 1 and lowerTriMatrix[1][1] = 5
5 
Column Iteration = 3, Column Number = 2, and Row Number = 1
The result of (rows >= columns) = 0 and lowerTriMatrix[1][2] = 6
0 

Row Iteration = 3, Row Number = 2
Column Iteration = 1, Column Number = 0, and Row Number = 2
The result of (rows >= columns) = 1 and lowerTriMatrix[2][0] = 7
7 
Column Iteration = 2, Column Number = 1, and Row Number = 2
The result of (rows >= columns) = 1 and lowerTriMatrix[2][1] = 8
8 
Column Iteration = 3, Column Number = 2, and Row Number = 2
The result of (rows >= columns) = 1 and lowerTriMatrix[2][2] = 9
9

C++ Program to Print Lower Triangle of a Matrix using a While Loop

#include<iostream>
using namespace std;

int main()
{
	int size, i, j, rows, columns;
	
	cout << "\nPlease Enter Matrix rows and Columns to find Lower Triangle =  ";
	cin >> i >> j;
	
	int lowerTriMatrix[i][j];
	
	cout << "\nPlease Enter the Matrix Items\n";
	for(rows = 0; rows < i; rows++)	{
		for(columns = 0; columns < i; columns++) {
			cin >> lowerTriMatrix[rows][columns];
		}		
	}

 	cout << "\nThe Result of the Lower Triangle Matrix is :\n";
 	rows = 0; 
 	while(rows < i)
  	{
  		cout << "\n";
  		columns = 0; 
   		while(columns < j)
    	{
    		if(rows >= columns)
    		{
    			cout << lowerTriMatrix[rows][columns] << " ";
			}
			else
			{
				cout << "0 ";
			}
			columns++;
   	 	}
   	 	rows++;
  	}	

 	return 0;
}

Please Enter Matrix rows and Columns to find Lower Triangle =  3 3

Please Enter the Matrix Items
1 2 3
9 8 7
4 7 6

The Result of the Lower Triangle Matrix is :

1 0 0 
9 8 0 
4 7 6