# 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 contain elements below principle diagonal including principle diagonal elements and rest of the elements are 0.
• Upper triangular matrix is a matrix which contain elements above principle diagonal including principle diagonal elements and rest of the elements are 0.

LOWER TRIANGULAR : UPPER TIRANGULAR : Examples :

Input : matrix = {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 = {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 matrix  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)              {                  cout << "0" << " ";              }              else             cout << matrix[i][j] << " ";          }          cout << endl;      }  }     // Function to form upper triangular marix  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)              {                  cout << "0" << " ";              }              else             cout << matrix[i][j] << " ";          }          cout << endl;      }  }     // Driver Code  int main()  {      int matrix = {{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;  }

## Java

 // Java program to print Lower   // triangular and Upper triangular  // matrix of an array  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   # matrix  def 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 marix  def 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 Code  matrix = [[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 array  using 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  ?>

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


This article is contributed by Rishabh Jain. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes arrow_drop_up

Improved By : jit_t, Shivi_Aggarwal

Article Tags :
Practice Tags :

3

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.