Program to check if matrix is lower triangular - GeeksforGeeks

26 Apr, 2021
Given a square matrix and the task is to check the matrix is in lower triangular form or not. A square matrix is called lower triangular if all the entries above the main diagonal are zero.  
Examples:  
Input : mat[4][4] = {{1, 0, 0, 0},
                     {1, 4, 0, 0},
                     {4, 6, 2, 0},
                     {0, 4, 7, 6}};
Output : Matrix is in lower triangular form.

Input : mat[4][4] = {{1, 0, 0, 0},
                     {4, 3, 0, 1},
                     {7, 9, 2, 0},
                     {8, 5, 3, 6}};
Output : Matrix is not in lower triangular form.
 
 
C++
Java
Python3
C#
PHP
Javascript
// Program to check lower// triangular matrix.#include <bits/stdc++.h>#define N 4using namespace std; // Function to check matrix is in// lower triangular form or not.bool isLowerTriangularMatrix(int mat[N][N]){    for (int i = 0; i < N; i++)        for (int j = i + 1; j < N; j++)            if (mat[i][j] != 0)                return false;    return true;} // Driver function.int main(){    int mat[N][N] = { { 1, 0, 0, 0 },                      { 1, 4, 0, 0 },                      { 4, 6, 2, 0 },                      { 0, 4, 7, 6 } };     // Function call    if (isLowerTriangularMatrix(mat))        cout << "Yes";    else        cout << "No";    return 0;}
// Java Program to check for// a lower triangular matrix.import java.io.*; class Lower_triangular{    int N = 4;     // Function to check matrix is    // in lower triangular form or not.    boolean isLowerTriangularMatrix(int mat[][])    {        for (int i = 0; i < N; i++)            for (int j = i + 1; j < N; j++)                if (mat[i][j] != 0)                    return false;         return true;    }     // Driver function.    public static void main(String args[])    {        Lower_triangular ob = new Lower_triangular();        int mat[][] = { { 1, 0, 0, 0 },                        { 1, 4, 0, 0 },                        { 4, 6, 2, 0 },                        { 0, 4, 7, 6 } };                                 // Function call        if (ob.isLowerTriangularMatrix(mat))            System.out.println("Yes");        else            System.out.println("No");    }} // This code is contributed by Anshika Goyal.
# Python3 Program to check# lower triangular matrix. # Function to check matrix# is in lower triangulardef islowertriangular(M):    for i in range(0, len(M)):        for j in range(i + 1, len(M)):            if(M[i][j] != 0):                    return False    return True     # Driver function.M = [[1,0,0,0],     [1,4,0,0],     [4,6,2,0],     [0,4,7,6]] if islowertriangular(M):    print ("Yes")else:    print ("No")     # This code is contributed by Anurag Rawat
// C# program to check for// a lower triangular matrix.using System; class Lower_triangular{    int N = 4;     // Function to check matrix is    // in lower triangular form or not.    bool isLowerTriangularMatrix(int[, ] mat)    {        for (int i = 0; i < N; i++)            for (int j = i + 1; j < N; j++)                if (mat[i, j] != 0)                    return false;         return true;    }     // Driver function.    public static void Main()    {        Lower_triangular ob = new Lower_triangular();        int[, ] mat = { { 1, 0, 0, 0 },                        { 1, 4, 0, 0 },                        { 4, 6, 2, 0 },                        { 0, 4, 7, 6 } };         // Function call        if (ob.isLowerTriangularMatrix(mat))            Console.WriteLine("Yes");        else            Console.WriteLine("No");    }} // This code is contributed by vt_m.
<?php// PHP Program to check lower// triangular matrix.$N = 4; // Function to check matrix is in// lower triangular form or not.function isLowerTriangularMatrix($mat){    global $N;    for ($i = 0; $i < $N; $i++)        for ($j = $i + 1; $j < $N; $j++)            if ($mat[$i][$j] != 0)                return false;    return true;} // Driver Code$mat = array(array( 1, 0, 0, 0 ),             array( 1, 4, 0, 0 ),             array( 4, 6, 2, 0 ),             array( 0, 4, 7, 6 ));      // Function callif (isLowerTriangularMatrix($mat))    echo("Yes");else    echo("No"); // This code is contributed by Ajit.?>
<script>// Java  script Program to check for// a lower triangular matrix.     let N = 4;     // Function to check matrix is    // in lower triangular form or not.    function isLowerTriangularMatrix(mat)    {        for (let i = 0; i < N; i++)            for (let j = i + 1; j < N; j++)                if (mat[i][j] != 0)                    return false;         return true;    }     // Driver function.                      let mat = [[ 1, 0, 0, 0 ],                        [ 1, 4, 0, 0 ],                        [ 4, 6, 2, 0 ],                        [ 0, 4, 7, 6 ]];                                 // Function call        if (isLowerTriangularMatrix(mat))            document.write("Yes");        else            document.write("No");          // contributed by sravan kumar</script>
Output:  
Yes
 
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