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Add QuadraticEquationSolver and test cases (#5619)
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@ -377,6 +377,7 @@
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* [PrimeFactorization](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PrimeFactorization.java)
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* [PrimeFactorization](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PrimeFactorization.java)
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* [PronicNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PronicNumber.java)
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* [PronicNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PronicNumber.java)
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* [PythagoreanTriple](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PythagoreanTriple.java)
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* [PythagoreanTriple](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/PythagoreanTriple.java)
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* [QuadraticEquationSolver](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/QuadraticEquationSolver.java)
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* [ReverseNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/ReverseNumber.java)
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* [ReverseNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/ReverseNumber.java)
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* [RomanNumeralUtil](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/RomanNumeralUtil.java)
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* [RomanNumeralUtil](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/RomanNumeralUtil.java)
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* [SecondMinMax](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SecondMinMax.java)
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* [SecondMinMax](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SecondMinMax.java)
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@ -0,0 +1,60 @@
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package com.thealgorithms.maths;
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/**
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* This class represents a complex number which has real and imaginary part
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*/
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class ComplexNumber {
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Double real;
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Double imaginary;
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ComplexNumber(double real, double imaginary) {
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this.real = real;
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this.imaginary = imaginary;
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}
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ComplexNumber(double real) {
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this.real = real;
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this.imaginary = null;
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}
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}
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/**
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* Quadratic Equation Formula is used to find
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* the roots of a quadratic equation of the form ax^2 + bx + c = 0
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*
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* @see <a href="https://en.wikipedia.org/wiki/Quadratic_equation">Quadratic Equation</a>
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*/
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public class QuadraticEquationSolver {
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/**
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* Function takes in the coefficients of the quadratic equation
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*
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* @param a is the coefficient of x^2
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* @param b is the coefficient of x
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* @param c is the constant
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* @return roots of the equation which are ComplexNumber type
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*/
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public ComplexNumber[] solveEquation(double a, double b, double c) {
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double discriminant = b * b - 4 * a * c;
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// if discriminant is positive, roots will be different
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if (discriminant > 0) {
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return new ComplexNumber[] {new ComplexNumber((-b + Math.sqrt(discriminant)) / (2 * a)), new ComplexNumber((-b - Math.sqrt(discriminant)) / (2 * a))};
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}
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// if discriminant is zero, roots will be same
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if (discriminant == 0) {
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return new ComplexNumber[] {new ComplexNumber((-b) / (2 * a))};
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}
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// if discriminant is negative, roots will have imaginary parts
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if (discriminant < 0) {
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double realPart = -b / (2 * a);
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double imaginaryPart = Math.sqrt(-discriminant) / (2 * a);
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return new ComplexNumber[] {new ComplexNumber(realPart, imaginaryPart), new ComplexNumber(realPart, -imaginaryPart)};
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}
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// return no roots
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return new ComplexNumber[] {};
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}
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}
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@ -0,0 +1,50 @@
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package com.thealgorithms.maths;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Test;
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public class QuadraticEquationSolverTest {
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private final QuadraticEquationSolver quadraticEquationSolver = new QuadraticEquationSolver();
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@Test
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public void testSolveEquationRealRoots() {
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// 4.2x^2 + 8x + 1.9 = 0
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double a = 4.2;
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double b = 8;
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double c = 1.9;
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ComplexNumber[] roots = quadraticEquationSolver.solveEquation(a, b, c);
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Assertions.assertEquals(roots.length, 2);
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Assertions.assertEquals(roots[0].real, -0.27810465435684306);
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Assertions.assertNull(roots[0].imaginary);
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Assertions.assertEquals(roots[1].real, -1.6266572504050616);
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Assertions.assertNull(roots[1].imaginary);
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}
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@Test
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public void testSolveEquationEqualRoots() {
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// x^2 + 2x + 1 = 0
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double a = 1;
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double b = 2;
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double c = 1;
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ComplexNumber[] roots = quadraticEquationSolver.solveEquation(a, b, c);
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Assertions.assertEquals(roots.length, 1);
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Assertions.assertEquals(roots[0].real, -1);
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}
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@Test
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public void testSolveEquationComplexRoots() {
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// 2.3x^2 + 4x + 5.6 = 0
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double a = 2.3;
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double b = 4;
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double c = 5.6;
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ComplexNumber[] roots = quadraticEquationSolver.solveEquation(a, b, c);
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Assertions.assertEquals(roots.length, 2);
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Assertions.assertEquals(roots[0].real, -0.8695652173913044);
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Assertions.assertEquals(roots[0].imaginary, 1.2956229935435948);
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Assertions.assertEquals(roots[1].real, -0.8695652173913044);
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Assertions.assertEquals(roots[1].imaginary, -1.2956229935435948);
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}
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}
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