diff --git a/DIRECTORY.md b/DIRECTORY.md index ad337f35fc8f..1cd30a336f24 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -377,6 +377,7 @@ * [PrimeFactorization](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PrimeFactorization.java) * [PronicNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PronicNumber.java) * [PythagoreanTriple](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PythagoreanTriple.java) + * [QuadraticEquationSolver](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/QuadraticEquationSolver.java) * [ReverseNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/ReverseNumber.java) * [RomanNumeralUtil](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/RomanNumeralUtil.java) * [SecondMinMax](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SecondMinMax.java) diff --git a/src/main/java/com/thealgorithms/maths/QuadraticEquationSolver.java b/src/main/java/com/thealgorithms/maths/QuadraticEquationSolver.java new file mode 100644 index 000000000000..cd654c5dc023 --- /dev/null +++ b/src/main/java/com/thealgorithms/maths/QuadraticEquationSolver.java @@ -0,0 +1,60 @@ +package com.thealgorithms.maths; + +/** + * This class represents a complex number which has real and imaginary part + */ +class ComplexNumber { + Double real; + Double imaginary; + + ComplexNumber(double real, double imaginary) { + this.real = real; + this.imaginary = imaginary; + } + + ComplexNumber(double real) { + this.real = real; + this.imaginary = null; + } +} + +/** + * Quadratic Equation Formula is used to find + * the roots of a quadratic equation of the form ax^2 + bx + c = 0 + * + * @see Quadratic Equation + */ +public class QuadraticEquationSolver { + /** + * Function takes in the coefficients of the quadratic equation + * + * @param a is the coefficient of x^2 + * @param b is the coefficient of x + * @param c is the constant + * @return roots of the equation which are ComplexNumber type + */ + public ComplexNumber[] solveEquation(double a, double b, double c) { + double discriminant = b * b - 4 * a * c; + + // if discriminant is positive, roots will be different + if (discriminant > 0) { + return new ComplexNumber[] {new ComplexNumber((-b + Math.sqrt(discriminant)) / (2 * a)), new ComplexNumber((-b - Math.sqrt(discriminant)) / (2 * a))}; + } + + // if discriminant is zero, roots will be same + if (discriminant == 0) { + return new ComplexNumber[] {new ComplexNumber((-b) / (2 * a))}; + } + + // if discriminant is negative, roots will have imaginary parts + if (discriminant < 0) { + double realPart = -b / (2 * a); + double imaginaryPart = Math.sqrt(-discriminant) / (2 * a); + + return new ComplexNumber[] {new ComplexNumber(realPart, imaginaryPart), new ComplexNumber(realPart, -imaginaryPart)}; + } + + // return no roots + return new ComplexNumber[] {}; + } +} diff --git a/src/test/java/com/thealgorithms/maths/QuadraticEquationSolverTest.java b/src/test/java/com/thealgorithms/maths/QuadraticEquationSolverTest.java new file mode 100644 index 000000000000..a2046511ddf5 --- /dev/null +++ b/src/test/java/com/thealgorithms/maths/QuadraticEquationSolverTest.java @@ -0,0 +1,50 @@ +package com.thealgorithms.maths; + +import org.junit.jupiter.api.Assertions; +import org.junit.jupiter.api.Test; + +public class QuadraticEquationSolverTest { + private final QuadraticEquationSolver quadraticEquationSolver = new QuadraticEquationSolver(); + + @Test + public void testSolveEquationRealRoots() { + // 4.2x^2 + 8x + 1.9 = 0 + double a = 4.2; + double b = 8; + double c = 1.9; + + ComplexNumber[] roots = quadraticEquationSolver.solveEquation(a, b, c); + Assertions.assertEquals(roots.length, 2); + Assertions.assertEquals(roots[0].real, -0.27810465435684306); + Assertions.assertNull(roots[0].imaginary); + Assertions.assertEquals(roots[1].real, -1.6266572504050616); + Assertions.assertNull(roots[1].imaginary); + } + + @Test + public void testSolveEquationEqualRoots() { + // x^2 + 2x + 1 = 0 + double a = 1; + double b = 2; + double c = 1; + + ComplexNumber[] roots = quadraticEquationSolver.solveEquation(a, b, c); + Assertions.assertEquals(roots.length, 1); + Assertions.assertEquals(roots[0].real, -1); + } + + @Test + public void testSolveEquationComplexRoots() { + // 2.3x^2 + 4x + 5.6 = 0 + double a = 2.3; + double b = 4; + double c = 5.6; + + ComplexNumber[] roots = quadraticEquationSolver.solveEquation(a, b, c); + Assertions.assertEquals(roots.length, 2); + Assertions.assertEquals(roots[0].real, -0.8695652173913044); + Assertions.assertEquals(roots[0].imaginary, 1.2956229935435948); + Assertions.assertEquals(roots[1].real, -0.8695652173913044); + Assertions.assertEquals(roots[1].imaginary, -1.2956229935435948); + } +}