链表的经典应用，程序在多项式相加同类项合并还有小的瑕疵，有待改进。
代码如下：
package 一元多项式计算器;
public class PolyNode {
private double a;
private int i;
PolyNode next;
public PolyNode(double a,int i){
this.a=a;
this.i=i;
this.next=null;
}
public PolyNode(){
this(0,0);
}
public double getA() {
return a;
}
public int getI() {
return i;
}
public void setA(double a) {
this.a = a;
}
public void setI(int i) {
this.i = i;
}
}
package 一元多项式计算器;
public class PolyList {
PolyNode head;
PolyNode current;
public PolyList(){
head=new PolyNode();
current=head;
head.next=null;
}
//是否为空
public boolean isEmpty(){
return head.next==null;
}
//这里只考虑按顺序插入元素
public void insert(PolyNode node){
current.next=node;
current=node;
}
//打印多项式
public String printS(){
StringBuilder s=new StringBuilder("");
StringBuilder a=new StringBuilder("");
StringBuilder i=new StringBuilder("");
StringBuilder theOne=new StringBuilder("");
current=head.next;
int count1=0;
int count2=0;
while(current!=null){
if(current.getA() == 0){
count1++;
}
count2++;
current = current.next;
}
if(count1 == count2){
s.append("0");
}else{
current=head.next;
while(current!=null){
a.delete(0, a.length());
i.delete(0, i.length());
theOne.delete(0, theOne.length());
if((current.getA()==1 || current.getA()==-1) && current.getI()!=0)
a.append("");
else if(current.getA() < 0){
a.append(String.valueOf((-current.getA())));
}else{
a.append(String.valueOf(current.getA()));
}
if(current.getI()==1)
{
i.append("");
theOne.append(a.toString()).append("x").append(i.toString());
} else if(current.getI()==0){
i.append("");
theOne.append(a.toString());
} else{
i.append(String.valueOf(current.getI()));
theOne.append(a.toString()).append("x^").append(i.toString());
}
if(current.getA() == 0){
s.append("");
}else{
if(current==head.next && current.getA()<0){
s.append("-").append(theOne.toString());
}else if(current==head.next && current.getA()>0){
s.append(theOne.toString());
}
else if(current.getA() < 0){
s.append(" - ").append(theOne.toString());
}else
s.append(" + ").append(theOne.toString());
}
current = current.next;
}
}
return s.toString();
}
//加法运算
public static PolyList add(PolyList p1,PolyList p2){
PolyList result=new PolyList();
//分别指向p1 p2的第一个元素
p1.current=p1.head.next;
p2.current=p2.head.next;
while(p1.current!=null && p2.current!=null){
if(p1.current.getI()==p2.current.getI()){
result.insert(new PolyNode(p1.current.getA()+p2.current.getA(),p1.current.getI()));
p1.current=p1.current.next;
p2.current=p2.current.next;
}
else if(p1.current.getI()<p2.current.getI()){
result.insert(p1.current);
p1.current=p1.current.next;
}else{
result.insert(p2.current);
p2.current=p2.current.next;
}
}
while(p1.current!=null){
result.insert(p1.current);
p1.current=p1.current.next;
}
while(p2.current!=null){
result.insert(p2.current);
p2.current=p2.current.next;
}
//return result;
result.current=result.head.next;
PolyNode tempPrevious=result.current;
PolyNode temp=result.current.next;
while(result.current.next!=null){
while(temp!=null)
{
if(temp.getI()!=result.current.getI())
{
temp=temp.next;
tempPrevious=tempPrevious.next;
}else{
result.current.setA(result.current.getA()+temp.getA());
tempPrevious.next=temp.next;
temp=temp.next;
}
}
result.current=result.current.next;
tempPrevious=result.current;
temp=result.current.next;
}
return result;
}
//减法运算
public static PolyList sub(PolyList p1,PolyList p2){
PolyList result=new PolyList();
p2.current = p2.head.next;
while(p2.current!=null){
p2.current.setA(-(p2.current.getA()));
p2.current=p2.current.next;
}
//System.out.println(p2.printS());
//分别指向p1 p2的第一个元素
p1.current=p1.head.next;
p2.current=p2.head.next;
while(p1.current!=null && p2.current!=null){
if(p1.current.getI()==p2.current.getI()){
result.insert(new PolyNode(p1.current.getA()+p2.current.getA(),p1.current.getI()));
p1.current=p1.current.next;
p2.current=p2.current.next;
}
else if(p1.current.getI()<p2.current.getI()){
result.insert(p1.current);
p1.current=p1.current.next;
}else{
result.insert(p2.current);
p2.current=p2.current.next;
}
}
while(p1.current!=null){
result.insert(p1.current);
p1.current=p1.current.next;
}
while(p2.current!=null){
result.insert(p2.current);
p2.current=p2.current.next;
}
return result;
}
//乘法运算
public static PolyList multiply(PolyList p1,PolyList p2){
PolyList result=new PolyList();
//分别指向p1 p2的第一个元素
p1.current=p1.head.next;
p2.current=p2.head.next;
while(p1.current!=null){
while(p2.current!=null)
{
double a=p1.current.getA()*p2.current.getA();
int i=p1.current.getI()+p2.current.getI();
result.insert(new PolyNode(a,i));
p2.current=p2.current.next;
}
p1.current=p1.current.next;
p2.current=p2.head.next;
}
//合并同类项
result.current=result.head.next;
PolyNode tempPrevious=result.current;
PolyNode temp=result.current.next;
PolyNode t = result.current.next;
while(result.current.next!=null){
while(temp!=null)
{
if(temp.getI()!=result.current.getI())
{
temp=temp.next;
tempPrevious=tempPrevious.next;
}else{
result.current.setA(result.current.getA()+temp.getA());
tempPrevious.next=temp.next;
temp=temp.next;
}
}
result.current=result.current.next;
tempPrevious=result.current;
temp=result.current.next;
}
return result;
}
//就地逆置单链表
public static void reverse(PolyList p_){
PolyNode p,q;
p = p_.head.next;
p_.head.next = null;
while(p!=null){
q = p.next;
p.next = p_.head.next;//让p.next变成p_.head.next;
p_.head.next = p;//让p_.head.next变成p;
p = q;//让p变成q;
}
}
}
package 一元多项式计算器;
import java.util.*;
public class Testclass {
public static void main(String[] args) {
// TODO Auto-generated method stub
while(true){
PolyList p1 = new PolyList();
PolyList p2 = new PolyList();
Scanner scan = new Scanner(System.in);
System.out.print("请输入要计算的第一个多项式的系数和指数，以0,0结束：");
double a = scan.nextDouble();
int i = scan.nextInt();
while(a!=0 || i!=0){
p1.insert(new PolyNode(a,i));
a = scan.nextDouble();
i = scan.nextInt();
}
System.out.println("您输入的第一个多项式为：");
System.out.println("p1 = " + p1.printS());
System.out.print("请输入要计算的第二个多项式的系数和指数，以0,0结束：");
a = scan.nextDouble();
i = scan.nextInt();
while(a!=0 || i!=0){
p2.insert(new PolyNode(a,i));
a = scan.nextDouble();
i = scan.nextInt();
}
System.out.println("您输入的第二个多项式为：");
System.out.println("p2 = " + p2.printS());
System.out.println("请按提示选择您想要进行的运算：");
System.out.println("0 -----> +");
System.out.println("1 -----> -");
System.out.println("2 -----> x");
int n;
n = scan.nextInt();
if(n == 0){
PolyList resultList= PolyList.add(p1, p2);
PolyList.reverse(resultList);
System.out.println("p1 + p2 = "+resultList.printS());
}else if(n == 1){
PolyList resultList= PolyList.sub(p1, p2);
PolyList.reverse(resultList);
System.out.println("p1 - p2 = "+resultList.printS());
}else{
PolyList resultList= PolyList.multiply(p1, p2);
//PolyList.reverse(resultList);
System.out.println("p1 x p2 = "+resultList.printS());
}
}
}
}
//还存在的bug：1-当系数为0的时候应该删去一整项； 已解决！
// 2-当一个多项式只有0时，应该输出一个0；已解决！
// 3-计算器的仿真界面。已解决！使用不方便！
// 4-合并同类项有空指针错误，待解决，错误数据如1 1 1 1 0 0+1 1 1 1 0 0；