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Commit a24450a

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piyushk77appgurueu
andauthored
feat: add determinant algorithm (#1438)
* feat: add determinant calculating algorithm * test: add self-tests for determinant algorithm * chore: add wikipedia info link * fix: change initialization to zero * fix: add error throw and general code improvements * fix: add error try and catch * fix: seperate the test loops of error cases * clean up a bit --------- Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
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‎Maths/Determinant.js

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/**
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* Given a square matrix, find its determinant using Laplace Expansion.
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* Time Complexity : O(n!)
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*
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* For more info: https://en.wikipedia.org/wiki/Determinant
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*
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* @param {number[[]]} matrix - Two dimensional array of integers.
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* @returns {number} - An integer equal to the determinant.
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*
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* @example
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* const squareMatrix = [
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* [2,3,4,6],
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* [5,8,9,0],
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* [7,4,3,9],
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* [4,0,2,1]
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* ];
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*
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* const result = determinant(squareMatrix);
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* // The function should return 858 as the resultant determinant.
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*/
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const subMatrix = (matrix, i, j) => {
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let matrixSize = matrix[0].length
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if (matrixSize === 1) {
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return matrix[0][0]
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}
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let subMatrix = []
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for (let x = 0; x < matrixSize; x++) {
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if (x === i) {
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continue
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}
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subMatrix.push([])
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for (let y = 0; y < matrixSize; y++) {
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if (y === j) {
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continue
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}
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subMatrix[subMatrix.length - 1].push(matrix[x][y])
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}
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}
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return subMatrix
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}
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const isMatrixSquare = (matrix) => {
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let numRows = matrix.length
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for (let i = 0; i < numRows; i++) {
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if (numRows !== matrix[i].length) {
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return false
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}
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}
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return true
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}
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const determinant = (matrix) => {
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if (
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!Array.isArray(matrix) ||
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matrix.length === 0 ||
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!Array.isArray(matrix[0])
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) {
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throw new Error('Input is not a valid 2D matrix.')
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}
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if (!isMatrixSquare(matrix)) {
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throw new Error('Square matrix is required.')
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}
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let numCols = matrix[0].length
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if (numCols === 1) {
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return matrix[0][0]
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}
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let result = 0
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let setIndex = 0
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for (let i = 0; i < numCols; i++) {
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result +=
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Math.pow(-1, i) *
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matrix[setIndex][i] *
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determinant(subMatrix(matrix, setIndex, i))
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}
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return result
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}
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export { determinant }

‎Maths/test/Determinant.test.js

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import { expect } from 'vitest'
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import { determinant } from '../Determinant'
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describe('Determinant', () => {
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test.each([
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[
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[
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[8, 1, 6],
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[1, 2, 3],
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[4, 7, 5]
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],
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-87
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],
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[
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[
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[2, 1, 0, 2],
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[1, 2, 4, 3],
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[0, 4, 7, 5],
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[4, 7, 9, 8]
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],
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25
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],
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[
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[
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[5, 9],
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[3, 7]
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],
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8
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],
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[
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[
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[7, 5, 1, 4, 3],
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[6, 8, 7, 9, 6],
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[9, 8, 0, 4, 7],
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[0, 3, 4, 7, 9],
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[3, 6, 2, 8, 8]
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],
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2476
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],
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[[[23]], 23]
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])(
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'Should return the determinant of the square matrix.',
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(matrix, expected) => {
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expect(determinant(matrix)).toEqual(expected)
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}
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)
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test.each([
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[
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[
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[1, 6],
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[1, 2, 3],
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[4, 7, 5]
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],
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'Square matrix is required.'
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],
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[[1, 3, 2, [5, 8, 6], 3], 'Input is not a valid 2D matrix.']
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])(
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'Should return the error message.',
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(matrix, expected) => {
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expect(() => determinant(matrix)).toThrowError(expected)
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}
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)
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})

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