/**
完成多项式的计算器，可以进行多项式的加法，减法，乘法三种运算。
*/
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.Stack;
public class ExpressionMain {
public static void main(String[] args) {
expressionCalculator();
}
private static void expressionCalculator() {
System.out.println("This is a polynomials program.\n" +
"Please enter a valid command:\n" +
"[?] Read a Polynomial.\n" +
"[=] Return a Polynomial.\n" +
"[+] Sum two Polynomial.\n" +
"[-] Difference two Polynomial。 \n" +
"[*] Mult one Polynomial with a term Polynomial.\n" +
"[Q] Quit.\n");
Scanner scanner = new Scanner(System.in);
boolean isTheWorldAlive = true;
Stack<Term> stack = new Stack<Term>();
while (isTheWorldAlive) {
System.out.println("Select command and presss <Enter>:");
String command = scanner.next();
if ("?".equals(command)) {
boolean isCurrentExpressionInProgress = true;
Term current = new Term();
boolean firstTime = true;
while (isCurrentExpressionInProgress) {
System.out.println("coefficient?");
int xishu = scanner.nextInt();
if (xishu != 0) {
System.out.println("exponent?");
int zhishu = scanner.nextInt();
if (zhishu != 0) {
if(firstTime){
current.setXishu(xishu);
current.setZhishu(zhishu);
firstTime = false;
}else{
Term temp = current;
while(temp.next != null){
temp = temp.next;
}
temp.next = new Term(xishu, zhishu);
}
} else {
System.out.println("The following has been pushed to Stack:");
System.out.println(current.toString());
stack.push(current);
isCurrentExpressionInProgress = false;
}
} else {
System.out.println("The following has been pushed to Stack:");
System.out.println(current.toString());
stack.push(current);
isCurrentExpressionInProgress = false;
}
}
} else if("+".equals(command)){
System.out.println(Expression.add(stack.pop(), stack.pop()));
}else if("-".equals(command)){
System.out.println(Expression.minus(stack.pop(), stack.pop()));
}else if("*".equals(command)){
System.out.println(Expression.mutiple(stack.pop(), stack.pop()));
}
else if ("Q".equalsIgnoreCase(command)) {
isTheWorldAlive = false;
}
}
}
}
class Term {
private int xishu;
private int zhishu;
Term next = null;
Term(){}
Term(int xishu, int zhishu){
this.xishu = xishu;
this.zhishu = zhishu;
this.next = null;
}
public int getXishu() {
return xishu;
}
public void setXishu(int xishu) {
this.xishu = xishu;
}
public int getZhishu() {
return zhishu;
}
public void setZhishu(int zhishu) {
this.zhishu = zhishu;
}
public String toString(){
String toString = xishu+"X^"+zhishu;
Term term = this.next;
while (term != null){
int nextXishu = term.getXishu();
toString = toString + ((nextXishu>0)?"+"+nextXishu:nextXishu)+"X^"+term.getZhishu();
term = term.next;
}
return toString;
}
}
class Expression {
public static Term add(Term t1, Term t2){
if(t1 == null){
return t2;
}else if(t2 == null){
return t1;
}else{
Term term = new Term();
if(t1.getZhishu() > t2.getZhishu()){
term.setZhishu(t1.getZhishu());
term.setXishu(t1.getXishu());
t1 = t1.next;
}else if(t1.getZhishu() == t2.getZhishu()){
term.setZhishu(t1.getZhishu());
term.setXishu(t1.getXishu() + t2.getXishu());
t1 = t1.next;
t2 = t2.next;
}else{
term.setZhishu(t2.getZhishu());
term.setXishu(t2.getXishu());
t2 = t2.next;
}
term.next = add(t1, t2);
return term;
}
}
public static Term minus(Term t1, Term t2){
if(t1 == null){
return t2;
}else if(t2 == null){
return t1;
}else{
Term term = new Term();
if(t1.getZhishu() > t2.getZhishu()){
term.setZhishu(t1.getZhishu());
term.setXishu(t1.getXishu());
t1 = t1.next;
}else if(t1.getZhishu() == t2.getZhishu()){
term.setZhishu(t1.getZhishu());
term.setXishu(t2.getXishu() - t1.getXishu());
t1 = t1.next;
t2 = t2.next;
}else{
term.setZhishu(t2.getZhishu());
term.setXishu(t2.getXishu() * -1);
t2 = t2.next;
}
term.next = minus(t1, t2);
return term;
}
}
public static Term mutiple(Term t1, Term t2){
Term temTerm;
if(t1.getXishu() < t2.getXishu()){
temTerm = t1;
t1 = t2;
t2 = temTerm;
}
List<Term> expressions = new ArrayList<Term>();
expressions.add(mutipleSingleTermToWholeTerm(t1, t2));
while (t2.next != null){
t2 = t2.next;
expressions.add(mutipleSingleTermToWholeTerm(t1, t2));
}
Term term = expressions.get(0);
for(int i=1; i<expressions.size(); i++){
term = add(term, expressions.get(i));
}
return term;
}
private static Term mutipleSingleTermToWholeTerm(Term t1, Term t2){
Term term = new Term();
term.setZhishu(t1.getZhishu() + t2.getZhishu());
term.setXishu(t1.getXishu() * t2.getXishu());
while (t1.next != null){
t1 = t1.next;
term.next = mutipleSingleTermToWholeTerm(t1, t2);
}
return term;
}
}
//运行效果：（展示实现两个多项式的加法）
