面向对象的第二次pta作业第一题：求一元二次方程

import java.util.Scanner;
public class Main {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input = new Scanner(System.in);
        double eqn[] = new double[3];
        eqn[0] = input.nextDouble();
        eqn[1] = input.nextDouble();
        eqn[2] = input.nextDouble();
        double roots[] = new double[2];
        if(eqn[0]==0) {
            System.out.println("Wrong Format");
            System.exit(0);
        }
        int n = solveQuadratic(eqn, roots);
        if(n == 2)
            System.out.printf("The equation has two roots: %.4f and %.4f", roots[0],roots[1]);
        else if(n == 1)
            System.out.printf("The equation has one root: %.4f",roots[0]);
        else
            System.out.println("The equation has no roots");

    }
    public static int solveQuadratic(double[] eqn, double[] roots) {
        int s = 0;
        double a=eqn[0],b=eqn[1],c=eqn[2];
        double d = b*b-4*a*c;
        if(d>0) {
            s=2;
            roots[0] = ((-1)*b+Math.sqrt(d))/2/a;
            roots[1] = ((-1)*b-Math.sqrt(d))/2/a;
        }
        else if(d==0) {
            s=1;
            if (b==0&&c==0) {
                roots[0] = 0.0000;
            }
            else
                roots[0] = (-1)*b/2/a;
        }
        return s;
        
    }

}

 

 

这次作业是把上一次的第一题用方法来写啦~

和c语言里面的函数差不多耶