Quadratic_Equation.java

/* 
Problem: Solving Quadratic equations in Java-
A program that prints all real solutions to quadratic equation ax^2+bx+c=0, if discriminant is negative displays a message "roots are imaginary". 
*/
import java.util.*;
import java.io.*;

public class Quadratic_Equation {
  public static void quadraticroots()
  {
    // value a, b, and c
    double a, b, c;
    double root1, root2;
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter coefficients of the equation:");
    System.out.print("Enter a: ");
    a = sc.nextDouble();
    System.out.println();
    System.out.print("Enter b: ");
    b = sc.nextDouble();
    System.out.println();
    System.out.print("Enter c: ");
    c = sc.nextDouble();
    System.out.println();
    // If a is 0, then equation is not quadratic, but linear
    if (a == 0) {
        System.out.println("Its a linear equation,Not a quadratic equation!");
        return;
      }
    // calculate the discriminant (b^2 - 4ac)
    double discriminant = b * b - 4 * a * c;
    // discriminant is greater than 0, real and distinct roots
    if (discriminant > 0) {
        root1 = (-b + Math.sqrt(discriminant)) / (2 * a);
        root2 = (-b - Math.sqrt(discriminant)) / (2 * a);
        System.out.println("Roots are real and distinct");
        System.out.format("root1 = %.2f and root2 = %.2f", root1, root2);
      }
    // discriminant is equal to 0, real and equal roots
    else if (discriminant == 0) {
        root1 = root2 = -b / (2 * a);
        System.out.println("Equal roots");
        System.out.format("root1 = root2 = %.2f;", root1);
      }
    // discriminant is less than zero, imaginary roots
    else {
        double real = -b / (2 * a);
        double imaginary = Math.sqrt(-discriminant) / (2 * a);
        System.out.println("Imaginary roots!");
        System.out.format("root1 = %.2f+%.2fi", real, imaginary);
        System.out.format("\nroot2 = %.2f-%.2fi", real, imaginary);
      }
  }
  public static void main(String[] args) {
    quadraticroots();
  }
}

/*
Sample Test Cases:

Test case 1:
Enter coefficients of the equation:
Enter a: 1

Enter b: -4

Enter c: 0

Roots are real and distinct
root1 = 4.00 and root2 = 0.00

Test case 2:
Enter coefficients of the equation:
Enter a: 7.2

Enter b: 5

Enter c: 9

Imaginary roots!
root1 = -0.35+1.06i
root2 = -0.35-1.06i

Test case 3:
Enter coefficients of the equation:
Enter a: 1

Enter b: -2

Enter c: 1

Equal roots
root1 = root2 = 1.00;

Time Complexity: O(1)
Space Complexity: O(1)
*/