java 使用LinkedList 实现多项式的相加相乘

Question

1定义类Term这个类将定义多项式的项。它应该有两个属性，系数和项的指数。
2.要使用LinkedList
3.使用toString 输出
4.使用scanner 输入输出

Answer 1

package com.learn.algorithm.ploy;

import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;


/**
 *多项式 相关 运算
 */
public class Ploy {

    public static void main(String[] args) {

        List<Node> La = init();
        List<Node> Lb = init();

        System.out.println(polyMulti(La,Lb));
    }


    private static List<Node> init() {
        List<Node> poly = new LinkedList<Node>();
        Scanner sc = new Scanner(System.in);

        System.out.println("请输入 系数和参数(例如  a,b 表示 aX^b,输入  0,0  结束。)：");
        while (true) {
            String line = sc.nextLine();
            if ( vaildate(line) ){
                String[] split = line.split(",");

                int coefficient = Integer.parseInt(split[0]);
                int exponential = Integer.parseInt(split[1]);

                if(coefficient == 0 && exponential == 0){
                    break;
                }

                poly.add(new Node(coefficient, exponential));
            } else {
                System.out.println("[" + line + "]输入有误");
            }
        }
        System.out.println(poly);
        return poly;
    }



    /**
     * 多项式加法
     * @param La
     * @param Lb
     * @return
     */
    public static List<Node> polyPlus(List<Node> La,List<Node> Lb){
        List<Node> Lc = new LinkedList<>();

        int Sa = La.size(),Sb=Lb.size(),ia=0,ib=0;

        while( ia < Sa && ib < Sb ){

            if ( La.get(ia).getExponential()< Lb.get(ib).getExponential()){
                Lc.add(La.get(ia));
                ia ++ ;
            } else if( La.get(ia).getExponential() == Lb.get(ib).getExponential() ){

                 int coe = La.get(ia).getCoefficient() + Lb.get(ib).getCoefficient();
                if( coe != 0 ){
                    Lc.add(new Node(coe,La.get(ia).getExponential()));
                }
                ia ++ ;
                ib ++;

            } else {
                Lc.add(Lb.get(ib));
                ib ++;
            }
        }

        while (ia < Sa) {
            Lc.add( La.get(ia++) );
        }
        while (ib < Sb) {
            Lc.add( Lb.get(ib++) );
        }

        return Lc ;

    }
    /**
     * 多项式加法(无序)
     * @param La
     * @param Lb
     * @return
     */
    public static List<Node> polyPlus_update(List<Node> La,List<Node> Lb){

        int Sa = La.size(),Sb=Lb.size(),ia=0,ib=0;

        while( ia < Sa ){

            Node node = La.get(ia);

            Node nodeByExp = getNodeByExp( Lb,node.getExponential() );

            if (nodeByExp != null) {
                if (node.getCoefficient() + nodeByExp.getCoefficient() == 0) {
                    Lb.remove(nodeByExp);
                } else{
                    nodeByExp.setCoefficient( node.getCoefficient() + nodeByExp.getCoefficient() );
                }
            } else {
                Lb.add(node);
            }
            ia ++;
        }


        return Lb ;

    }

    /**
     * 多项式乘法
     * @param La
     * @param Lb
     * @return
     */
    public static List<Node> polyMulti(List<Node> La,List<Node> Lb){
        List<Node> Lc = new LinkedList<>();
        int Sa = La.size(),Sb=Lb.size(),ia=0,ib=0;

        while( ia < Sa ){

            ib = 0;

            Node Na = La.get(ia);

            while (ib < Sb) {

                Node Nb = Lb.get(ib);

                int exp = Nb.getExponential() + Na.getExponential();//指数相加
                int coe = Nb.getCoefficient() * Na.getCoefficient();//系数相乘

                Node nodeByExp = getNodeByExp( Lc, exp);

                if (nodeByExp != null) {
                    if (coe + nodeByExp.getCoefficient() == 0) {
                        Lc.remove(nodeByExp);
                    } else{
                        nodeByExp.setCoefficient( coe+ nodeByExp.getCoefficient() );
                    }
                } else {
                    Lc.add(new Node(coe,exp));
                }
                ib ++ ;
            }

            ia ++;
        }


        return Lc ;

    }




    /**
     * 根据系数 寻找对应的项，没有则返回null
     * @param p
     * @param exp
     * @return
     */
    public static Node getNodeByExp(List<Node> p,Integer exp){
        if (exp == null || p == null ){
            return null;
        }

        for (Node node : p) {
            if (node.exponential == exp) {
                return node;
            }
        }
        return null;

    }


    /**
     * 验证输入字符串的合法性
     * @param s
     * @return
     */
    public static boolean vaildate(String s){
        return s.matches("[-]{0,1}[0-9]+[,]{1}[0-9]+");
    }
}


/**实体类
 *
 */
class Node {

    Integer coefficient =0; //系数
    Integer exponential  =0; //指数

    public Node(Integer coefficient,Integer exponential){
        this.coefficient = coefficient;
        this.exponential = exponential;
    }

    public Integer getCoefficient() {
        return coefficient;
    }

    public void setCoefficient(Integer coefficient) {
        this.coefficient = coefficient;
    }

    public Integer getExponential() {
        return exponential;
    }

    public void setExponential(Integer exponential) {
        this.exponential = exponential;
    }


    @Override
    public String toString() {
        return this.coefficient.toString() + "X^" + this.exponential.toString() ;
    }
}