polynomial.java

Java是最优秀的高级编程语言之一,多项式的加法运算,体现了链表数据结构的优势.

/**
 * @(#)Polynomial.java
 *
 *
 * @author 
 * @version 1.00 2006/10/25
 */
package Polynomial;
import java.io.*;
import java.lang.*;
public class Polynomial {
    private LinkedList terms;
    private LinkedListItr itr;
    public Polynomial() {
    	zeroPolynomial();
    	itr=terms.zeroth();
    }
/** This method is to initialize the polynomial
 **/    
    public void zeroPolynomial(){
    	terms=new LinkedList();
    }
    public LinkedListItr getFirst(){
    	return itr;
    }
    public void print(){
    	LinkedListItr itr=terms.first();
    	CoefAndExp p=null;
    	if(itr==null)
    		System.out.println("The result of adding these two polynomial is zero.");
    		else{
    			p=itr.retrieve();
    			p.print(true);
    			itr.advance();
    			for(;!itr.isPastEnd();itr.advance()){
    				p=itr.retrieve();
    				p.print(false);
    			}
    				System.out.println();
    		}
    }	
    private void build(int[] coef,int[] exp){
    	CoefAndExp parameter;
    	LinkedListItr itr=terms.zeroth();
    	for(int i=0;i<coef.length&&exp[i]!=-1;i++){
    		if(exp[i]>0){
    		parameter=new CoefAndExp(coef[i],exp[i]);
    		terms.insert(parameter,itr);
    		itr.advance();
    		}
    	else if(exp[i]==0){
    		parameter=new CoefAndExp(coef[i],0);
    	    itr.advance();
    	    terms.insert(parameter,itr);
    	}
    	}
    }
    public void read(){
    	String poly="";
    	int length=0;
    	char operator='1';
    	boolean positive=false;
    	int next=0;
    	int start=0;
    	int i=0;
    	System.out.println("Please enter a polynomial(such as 6x^5+2x^2-x+2):");
    	BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
    	try{
    		poly=in.readLine();
    	}catch(IOException e){}
    	int[] coef=new int[poly.length()];
    	int[] exp=new int[poly.length()];
    	for(int j=0;j<poly.length();j++)
    		exp[j]=-1;
		while(next!=-1&&poly.length()>1&&next!=poly.length()-1){
			next=0;
			next=poly.indexOf("x",next);
			if(next!=-1){
			operator=poly.charAt(0);
			if(operator=='+'){
				positive=true;
				start=1;
			}
				else if(operator=='-'){
					positive=false;
					start=1;
				}
					 else if(operator<='9'&&operator>='1')
					 	positive=true;
			if(start==next)
				coef[i]=1;
				else if(start!=next){
					coef[i]=Integer.parseInt(poly.substring(start,next));
					if(!positive)
						coef[i]=-coef[i];
				}
			if(next==poly.length()-1){
				exp[i]=1;
				break;
			}
			next++;
		    if(poly.charAt(next)=='^'){	
		    	start=next+1;
		    	next=start;
		    	operator=poly.charAt(next);
		        for(;operator!='+'&&operator!='-'&&next!=poly.length()-2;)
		        	operator=poly.charAt(++next);
		        exp[i]=Integer.parseInt(poly.substring(start,next));
		    }	
		    	else
		    		exp[i]=1;
			}
			if(next!=-1)
			poly=poly.substring(next);
			start=0;
			i++;
		}
		start=0;
		next=0;
		 if(poly.indexOf("x",0)==-1){
		 	operator=poly.charAt(0);
		 	if(operator=='+')
		 		positive=true;
		 		else positive=false;
		 		start++;
		 		coef[i]=Integer.parseInt(poly.substring(start));
		 		exp[i]=0;
		 		if(!positive)
		 			coef[i]=-coef[i];
		 			
	}
	}
	public void add(Polynomial rhs){
        	LinkedListItr itr1,itr2,itr3;
        	itr1=terms.zeroth();
        	itr2=terms.first();
        	itr3=rhs.getFirst();
        	CoefAndExp p1=null,p2=null;
        	if(itr1.isPastEnd()&&!itr3.isPastEnd()){
        		rhs.print();
        		return ;
        		}
        		else 
        			 if(itr1.isPastEnd()&&itr3.isPastEnd())
        			 	System.out.println("You have input nothing.");
        			 	else 
        			 		if(!itr1.isPastEnd()&&itr.isPastEnd())
        			 			print();
              else{
              	for(;!itr2.isPastEnd()&&!itr3.isPastEnd();itr2.advance()){
              			p1=itr2.retrieve();
              			p2=itr3.retrieve();
              			if(p1.equal(p2)==0){
              				p1.add(p2.getCoef());
              				itr3.advance();
              				if(p1.getCoef()==0)
              					terms.remove(p1);
              					itr2.advance();
              					}
              					else if(p1.equal(p2)==-1){
              						terms.insert(p2,itr1);
              						itr1=itr2;
              						itr2.advance();
              						itr3.advance();
              						}
              						else{
              							itr1=itr2;
              							itr2.advance();
              						}
              			
              	}
    }
}
}