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# Program to print Lower triangular and Upper triangular matrix of an array

Prerequisite – Multidimensional Arrays in C / C++
Given a two dimensional array, Write a program to print lower triangular matrix and upper triangular matrix.

• Lower triangular matrix is a matrix which contains elements below principal diagonal including principal diagonal elements and rest of the elements are 0.
• Upper triangular matrix is a matrix which contains elements above principal diagonal including principal diagonal elements and rest of the elements are 0.

LOWER TRIANGULAR :

UPPER TRIANGULAR :

Examples :

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

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

Steps:

1. For lower triangular matrix, we check the index position i and j i.e. row and column respectively. If column position is greater than row position we simply make that position 0.
2. For upper triangular matrix, we check the index position i and j i.e. row and column respectively. If column position is smaller than row position we simply make that position 0.

## C++

 // C++ program to print Lower // triangular and Upper triangular// matrix of an array#include  using namespace std;  // Function to form // lower triangular matrixvoid lower(int matrix[3][3], int row, int col){    int i, j;    for (i = 0; i < row; i++)    {        for (j = 0; j < col; j++)        {            if (i < j)            {                cout << "0" << " ";            }            else            cout << matrix[i][j] << " ";        }        cout << endl;    }}  // Function to form upper triangular matrixvoid upper(int matrix[3][3], int row, int col){    int i, j;          for (i = 0; i < row; i++)    {        for (j = 0; j < col; j++)        {            if (i > j)            {                cout << "0" << " ";            }            else            cout << matrix[i][j] << " ";        }        cout << endl;    }}  // Driver Codeint main(){    int matrix[3][3] = {{1, 2, 3},                         {4, 5, 6},                         {7, 8, 9}};    int row = 3, col = 3;          cout << "Lower triangular matrix: \n";    lower(matrix, row, col);          cout << "Upper triangular matrix: \n";    upper(matrix, row, col);              return 0;}

## C

 // C program to print lower triangular and upper triangular matrix#include   // Function to print lower triangular matrixvoid lower (int a[3][3], int r, int c){  for(int i = 0; i < r; i++)  {    for(int j = 0; j < c; j++)    {      if(i > j)        printf("0");      else      printf("%d" , a[i][j]);      printf(" ");    }    printf("\n");  }}//Function to print upper triangular matrixvoid upper (int a[3][3], int r, int c){   for(int i = 0; i < r; i++)  {    for(int j = 0; j < c; j++)    {      if(i < j)        printf("0");      else      printf("%d" , a[i][j]);      printf(" ");    }    printf("\n");  }}int main() {    // code  int r = 3, c = 3;  int a[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};     printf("\nLower Triangular Matrix is  :\n");  lower(a, r, c);  printf("\nUpper Triangular Matrix is  :\n");  upper(a, r, c);    return 0;}  // This code is contributed by aayushi2402.

## Java

 // Java program to print Lower // triangular and Upper triangular// matrix of an arrayimport java.io.*;public class GFG{    // method to form lower     // triangular matrix    static void lower(int matrix[][],                       int row, int col)    {        int i, j;        for (i = 0; i < row; i++)        {            for (j = 0; j < col; j++)            {                if (i < j)                {                    System.out.print("0" + " ");                }                else                System.out.print(matrix[i][j] + " ");            }            System.out.println();        }    }          // Method to form upper    // triangular matrix    static void upper(int matrix[][],                       int row, int col)    {        int i, j;        for (i = 0; i < row; i++)        {            for (j = 0; j < col; j++)            {                if (i > j)                {                    System.out.print("0" + " ");                }                else                System.out.print(matrix[i][j] + " ");            }            System.out.println();        }    }           // Driver Code    public static void main(String args[])    {        int matrix[][] = {{1, 2, 3},                           {4, 5, 6},                           {7, 8, 9}};        int row = 3, col = 3;                  System.out.println("Lower triangular matrix: ");        lower(matrix, row, col);                  System.out.println("Upper triangular matrix: ");        upper(matrix, row, col);    }}

## Python3

 # Python3 program to print Lower # triangular and Upper triangular# matrix of an array  # Function to form lower triangular # matrixdef lower(matrix, row, col):            for i in range(0, row):              for j in range(0, col):                      if (i < j):                              print("0", end = " ");                          else:                print(matrix[i][j],                        end = " " );                  print(" ");      # Function to form upper triangular matrixdef upper(matrix, row, col):      for i in range(0, row):              for j in range(0, col):                      if (i > j):                print("0", end = " ");                          else:                print(matrix[i][j],                        end = " " );                  print(" ");  # Driver Codematrix = [[1, 2, 3],           [4, 5, 6],           [7, 8, 9]];row = 3;col = 3;      print("Lower triangular matrix: ");lower(matrix, row, col);      print("Upper triangular matrix: ");upper(matrix, row, col);          # This code is contributed by# Shivi_Aggarwal

## C#

 // C# program to print  // Lower triangular and// Upper triangular// matrix of an arrayusing System;  class GFG{    // method to form lower     // triangular matrix    static void lower(int [,]matrix,                       int row, int col)    {        int i, j;        for (i = 0; i < row; i++)        {            for (j = 0; j < col; j++)            {                if (i < j)                {                    Console.Write("0" + " ");                }                else                Console.Write(matrix[i, j] + " ");            }            Console.WriteLine();        }    }          // Method to form upper    // triangular matrix    static void upper(int [,]matrix,                       int row, int col)    {        int i, j;        for (i = 0; i < row; i++)        {            for (j = 0; j < col; j++)            {                if (i > j)                {                    Console.Write("0" + " ");                }                else                Console.Write(matrix[i, j] + " ");            }        Console.WriteLine();        }    }          // Driver Code    static public void Main ()    {        int [,]matrix = {{1, 2, 3},                         {4, 5, 6},                         {7, 8, 9}};        int row = 3, col = 3;                  Console.WriteLine("Lower triangular matrix: ");        lower(matrix, row, col);                  Console.WriteLine("Upper triangular matrix: ");        upper(matrix, row, col);    }}  // This code is contributed by ajit

## PHP

  $j) { echo "0" , " "; } else echo $matrix[$i][$j] ," ";        }    echo "\n";    }}  // Driver Code$matrix = array (array (1, 2, 3), array (4, 5, 6), array (7, 8, 9));$row = 3; $col = 3;  echo "Lower triangular matrix: \n";lower($matrix, $row, $col);  echo "Upper triangular matrix: \n";upper($matrix, $row, \$col);      // This code is contributed by jit_t?>

## Javascript

 

Output

Lower triangular matrix:
1 0 0
4 5 0
7 8 9
Upper triangular matrix:
1 2 3
0 5 6
0 0 9 

Time Complexity: O(row x col)
Auxiliary Space: O(1), since no extra space has been taken.

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