题解 | #计算一元二次方程#

/*
    x1 = (-b + sqrt(b*b-4ac) )/ 2*a
*/
import java.util.Scanner;
public class Main {
    
    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        while(sc.hasNextDouble()) {
            double a = sc.nextDouble();
            double b = sc.nextDouble();
            double c = sc.nextDouble();
            double delta = Math.pow(b,2) - 4 * a * c;
            if(a == 0) {
                System.out.println("Not quadratic equation");
            } else if(delta == 0) {
                double result = (-1 * b) / (2 * a);
                System.out.println("x1=x2=" + String.format("%.2f",result));
            } else if(delta > 0) {
                double x1 = (-1*b + Math.sqrt(delta)) / (2*a);
                double x2 = (-1*b - Math.sqrt(delta)) / (2*a);
                if(x1 > x2) {
                    double temp = x1;
                    x1 = x2;
                    x2 = temp;
                }
                System.out.println("x1=" + String.format("%.2f", x1) + ";x2=" + String.format("%.2f", x2));
            } else if(delta < 0) {
                double shi;
                if(b == 0) {
                    shi = 0;
                } else {
                    shi = (-1 * b) / (2 * a);
                }
                double xu = Math.sqrt(-1 * delta) / (2 * a);
                System.out.print("x1=" + String.format("%.2f", shi) + "-" + String.format("%.2f", xu) + "i;");
                System.out.println("x2=" + String.format("%.2f", shi) + "+" + String.format("%.2f", xu) + "i");
            }
        }
    }
}