java - 关于打印多项式

Question

这是存储和评估输入数字多项式的类的一部分这是方法

public class Polynomial{
int coef,power;

public Polynomial(int maxPower){
}

public void setTerm(int coefficient, int power) {
    this.coef = coefficient;
    this.power = power;
}

以及main方法中的入参

public static void main(String[] args){
    Polynomial q = new Polynomial(2);
    q.setTerm(2, 0);
    q.setTerm(0, 1);
    q.setTerm(3, 2);
    System.out.println(q);
}

还有一个 toString 方法可以像这样打印出多项式

public String toString(){
    return 
}

我一直遇到 setTerm 方法只读取最后一个输入参数 q.setTerm(3,2) 的问题，我认为前两个被替换了。我能做什么？

Answer 1

因此在您的示例中，我们必须记住之前看到的术语。

我将按如下方式通过 map 完成。

import java.util.HashMap;
import java.util.Map;

/**
 * Created by arunavs on 9/28/16.
 */
public class Polynomial {

    // Key is power, value is coeff.
    private Map<Integer, Integer> powerToCoeffMap = new HashMap<>();

    // Maximal power allowed for polynomial.
    private int maxPower;


    public Polynomial(int maxPower){
        this.maxPower = maxPower;
    }

    public void setTerm(int coefficient, int power) {
        if (power > maxPower) {
           // throw some exception here. 
        }
        powerToCoeffMap.put(power, coefficient);
    }

    // terms may be rearranged in output. 
    public String toString() {
        StringBuilder builder = new StringBuilder();
        powerToCoeffMap.forEach((power, coeff) -> {builder.append(coeff + "x^" + power+ " ");});
        return builder.toString();
     }

        public static void main(String args[]) {
            Polynomial q = new Polynomial(2);
            q.setTerm(2, 0);
            q.setTerm(0, 1);
            q.setTerm(3, 2);
        System.out.println(q);
    }
}

输出:2x^0 0x^1 3x^2

希望对您有所帮助。