JavaScript Program to check if matrix is lower triangular

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.

// JavaScript 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))
    console.log("Yes");
else
    console.log("No");
// contributed by sravan kumar

Yes

Complexity Analysis:

• Time Complexity: O(n²), where n represents the number of rows and columns of the given matrix.
• Auxiliary Space: O(1), no extra space is required, so it is a constant.

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