JavaScript: Check whether a given matrix is lower triangular or not

JavaScript Basic: Exercise-121 with Solution

Check if Matrix is Lower Triangular

Write a JavaScript program to check whether a given matrix is lower triangular or not.

Note: A square matrix is called lower triangular if all the entries above the main diagonal are zero.

Sample Solution:

JavaScript Code:

// Function to check if a matrix is a lower triangular matrix
function lower_triangular_matrix(user_matrix) {
    for (var i = 0; i < user_matrix.length; i++) {
        for (var j = 0; j < user_matrix[0].length; j++) {
            // If element is above the main diagonal and not equal to zero, return false
            if (j > i && user_matrix[i][j] !== 0) {
                return false;
            }	
        }
    }
    return true; // Matrix is lower triangular
}

// Test cases
console.log(lower_triangular_matrix([[1, 0, 0],[2, 0, 0], [0, 3, 3]])); // Output: true (Lower triangular matrix)
console.log(lower_triangular_matrix([[1, 0, 1],[2, 0, 0], [0, 3, 3]])); // Output: false (Not a lower triangular matrix)

Output:

true
false

Live Demo:

See the Pen javascript-basic-exercise-121 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to check if a matrix is a lower triangular matrix
const lower_triangular_matrix = (user_matrix) => {
    for (let i = 0; i < user_matrix.length; i++) {
        for (let j = 0; j < user_matrix[0].length; j++) {
            // If element is above the main diagonal and not equal to zero, return false
            if (j > i && user_matrix[i][j] !== 0) {
                return false;
            }
        }
    }
    return true; // Matrix is lower triangular
};

// Test cases
console.log(lower_triangular_matrix([[1, 0, 0],[2, 0, 0], [0, 3, 3]])); // Output: true (Lower triangular matrix)
console.log(lower_triangular_matrix([[1, 0, 1],[2, 0, 0], [0, 3, 3]])); // Output: false (Not a lower triangular matrix)

For more Practice: Solve these Related Problems:

• Write a JavaScript program that checks if a square matrix is lower triangular by confirming all elements above the main diagonal are zero.
• Write a JavaScript function that iterates over a matrix and returns true if every element with a column index greater than its row index is zero.
• Write a JavaScript program that validates whether a matrix is lower triangular by comparing each element's row and column indices.

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