helloworld.java

import java.io.IOException;
import java.util.Scanner;
//first change
class node{
	public int quotiety = 1;//系数，正整数
	public char str[] = new char[26];//只能以单个字母作为变量
	public int exponential[] = new int[26];//次数，只支持10以下的正整数
	public int len = 0;
	public node next;
}

class Multinomial{
	public void quick_sort(node TempNode,int l, int r){//排序函数，对字符数组排序，方便合并同类项
	    if (l < r)
	    {
	        int i = l, j = r, x = TempNode.exponential[l];char y = TempNode.str[l];
	        while (i < j)
	        {
	            while(i < j && TempNode.str[j] >= y)
	                j--;
	            if(i < j){
	            	TempNode.exponential[i] = TempNode.exponential[j];
	            	TempNode.str[i] = TempNode.str[j];
	                i++;
	            }
	            while(i < j && TempNode.str[i] < y)
	                i++;
	            if(i < j){
	            	TempNode.exponential[j] = TempNode.exponential[i];
	            	TempNode.str[j] = TempNode.str[i];
	            	j--;
	            }
	        }
	        TempNode.exponential[i] = x;
	        TempNode.str[i] = y;
	        quick_sort(TempNode,l, i - 1); // 递归调用
	        quick_sort(TempNode,i + 1, r);
	    }
	}
	public int expression(char ch) throws IOException{//读入函数并建立链表储存数据
		node temp = head;char pre_ch = '!';int i,num=3;int index = 0;
		//pre_ch表示上一个变量名
		//num = 0 表示上个是变量或结点开头;num = 1 表示上个是'^';num = 2表示上个是数字;num = 3表示上一个是运算符
		if(ch=='\n')
			return 0;
		do{
			if(ch == '*'){
				num = 3;
			}
			else if(ch == '+'){
				temp.len = index;
				quick_sort(temp,0,temp.len-1);
				index = 0;
				temp.next = new node();
				temp = temp.next;
				num = 3;
			}
			else if(ch == '-'){
				if(pre_ch=='!'){
					temp.quotiety = -1;num = 3;
				}
				else{
					temp.len = index;
					quick_sort(temp,0,temp.len-1);
					index = 0;
					temp.next = new node();
					temp = temp.next;
					temp.quotiety = -1;
					num = 3;
				}
			}
			else if(ch == '^'){
				if(!((65 <= pre_ch && pre_ch <= 90)||(97 <= pre_ch && pre_ch <= 122))){
					System.out.println("输入不合法");
					return -1;
				}
				num = 1;
			}
			else if(48 <= ch && ch <= 57){//字母在前数字在后时，不能省略'*'
				if(num == 3){
					temp.quotiety = temp.quotiety*(ch-48);
				}
				else if(num == 1){
					for(i=0;i<index;i++){
						if(pre_ch != temp.str[i])
							continue;
						else{
							temp.exponential[i]+=(ch-48-1);
							break;
						}
					}
					i=0;
					num = 1;
				}
				else if(num == 2){
					if(temp.quotiety<0)
						temp.quotiety = (temp.quotiety)*10-(ch-48);
					else
						temp.quotiety = (temp.quotiety)*10+(ch-48);
				}
				num = 2;
			}
			else if((65 <= ch && ch <= 90)||(97<=ch && ch <= 122)){
				for(i=0;i<index;i++){
					if(ch != temp.str[i])
						continue;
					else{
						temp.exponential[i]++;
						break;
					}
				}
				if(i == index){
					temp.str[index] = ch;
					temp.exponential[index] = 1;
					index++;
					i = 0;
				}
				num = 0;
				pre_ch = ch;
			}
			else{
				System.out.print("输入不合法");
			}
		ch = (char)System.in.read();
		if(ch=='\r'){
			temp.len = index;
			quick_sort(temp,0,temp.len-1);
			return 0;
		}
		}while(ch!='\r');
		return 0;
	}

	public void combining(node Node){//合并同类项
		node NowNode = Node;
		node TempNode;
		node Temp_preNode;
		if(Node.next == null){
			return;
		}
		int i,counter; 
		do{
			TempNode = NowNode.next;Temp_preNode = NowNode;
			while(TempNode != null){
				String s = String.valueOf(NowNode.str);String t = String.valueOf(TempNode.str);
				if(s.equals(t)){
					counter = 0;
					for(i=0;i<NowNode.len;i++){
						if(NowNode.exponential[i]==TempNode.exponential[i]){
							counter++;
						}
						else
							break;
					}
					if(counter == NowNode.len){
						NowNode.quotiety += TempNode.quotiety;
						Temp_preNode.next = TempNode.next;
						TempNode = Temp_preNode.next;
						continue;
					}
					Temp_preNode = Temp_preNode.next;
					TempNode = TempNode.next;
				}
				else{
					Temp_preNode = Temp_preNode.next;
					TempNode = TempNode.next;
				}
			}
			NowNode = NowNode.next;
		}while(NowNode != null);
		do{
			if(Node.next==null)
				break;
			if(Node.len != 0){
				Node = Node.next;
			}
			else{
				node temp = Node;
				while(Node.next != null){
					if(Node.next.len == 0){
						temp.quotiety += Node.next.quotiety;
						Node.next = Node.next.next;
					}
					else{
						Node = Node.next;
					}
				}
			}
		}while(Node.next !=null);
	}
	public void simplify(char ch,int num){//赋值
		node TempNode = forother;
		do{
			for(int i=0;i<TempNode.len;i++){
				if(TempNode.str[i]==ch){
					TempNode.quotiety*=(num<<(TempNode.exponential[i]-1));
					TempNode.exponential[i] = 0;
					break;
				}
			}
			int count = 0;
			for(int i=0;i<TempNode.len;i++){
				count+=TempNode.exponential[i];
			}
			if(count == 0){
				TempNode.len = 0;
			}
			TempNode = TempNode.next;
		}while(TempNode!=null);
	}
	public void derivative(char x){//求导
		node t = forother;
		node h;
		h=t;
		int i=0;
		while(t!=null && i<=t.len){//求导函数
			if(t.str[i]==x ){
				t.quotiety*=t.exponential[i];
				t.exponential[i]-=1;
				int count = 0;
				for(int k=0;k<t.len;k++){
					count+=t.exponential[k];
				}
				if(count == 0){
					t.len = 0;
				}
				t=t.next;
				i=0;
				continue;
			}
			i++;
			if (i>=t.len ){//找不到x
				t.quotiety=0;
				t=t.next;
				i=0;
			}
		}
		t=h;
	}
	public void Print(node t){
		String res="";
		while(t!=null){
			if(t.quotiety!=0){//系数不为0，才有东西输出
				int s = 0;
				for(int i=0;i<t.len;i++){
					s+=t.exponential[i];
				}
				if(t.len==0||s==0){//字符串长度为0或者所有字符的次数都为0，此时
					res+=String.valueOf(t.quotiety);
				}
				else{
					if(t.quotiety!=1){
						if(t.quotiety == -1)
							res+="-";
						else
							res+=String.valueOf(t.quotiety);
					}
					for(int temp=0;temp<t.str.length;temp++)
					{
						if(t.exponential[temp]!=0){//判未知数输出条件
							res+=String.valueOf(t.str[temp]);
							if(t.exponential[temp]!= 1){//判次数输出条件
								res+="^";
								res+=String.valueOf(t.exponential[temp]);
							}
						}
					}
				}
			}
			if(t.next!=null && t.next.quotiety>0 && !res.equals("")){
				res+="+";
			}
			t=t.next;
		}
		if(res.length()!=0)
			System.out.println(res);
		else
			System.out.println(0);
	}

	public void mulcopy(){//创建一个镜像链表
		node temphead=head;
		node tempfor=forother;
		do{
			tempfor.quotiety=temphead.quotiety;
			tempfor.len=temphead.len;
			for(int i=0;i<temphead.len;i++){
				tempfor.exponential[i]=temphead.exponential[i];
				tempfor.str[i]=temphead.str[i];
			}
			if(temphead.next!=null){
				temphead=temphead.next;
				tempfor.next = new node();
				tempfor=tempfor.next;
			}
			else
				break;
		}while (true);
	}
	
	public node head = new node();//储存链表的头指针
	public node forother = new node();//镜像链表的头指针
}

public class helloworld {
	public static void main(String[] args) throws IOException{
		char ch;Multinomial multinomial1 = null;
		Scanner s=new Scanner(System.in);
		System.out.println("input something");
		while(true){
			ch = (char)System.in.read();
			if(ch == '!'){
				if(multinomial1!=null){
					String cmd=s.nextLine();
					char nd='y';//随便初始化一个
					if(cmd.length()>2 && cmd.substring(0,3).equals("end")){
						break;
					}
					else if (cmd.length()>2 && cmd.substring(0,3).equals("d/d")){
						nd=cmd.charAt(3);
						multinomial1.derivative(nd);
						multinomial1.combining(multinomial1.forother);
						multinomial1.Print(multinomial1.forother);
					}
					else if (cmd.length()>8 && cmd.substring(0, 9).equals("simplify ")){
						String now= cmd.substring(9);
						String[] cmdlist=now.split(" ");
						String[] cmdsplit;
						for(int j=0;j<cmdlist.length;j++){
							cmdsplit=cmdlist[j].split("=");
							char chnow;
							int numnow;
							chnow=cmdsplit[0].charAt(0);
							numnow=Integer.valueOf(cmdsplit[1]);
							multinomial1.simplify(chnow,numnow);
						}
						multinomial1.combining(multinomial1.forother);
						multinomial1.Print(multinomial1.forother);
					}
					else{
						System.out.println("输入的命令不合法，请重新输入");
					}
				}
				else{
					System.out.println("多项式为空，请先输入多项式");
					s.nextLine();
				}
			}
			else{
				multinomial1 = new Multinomial();
				int num = multinomial1.expression(ch);
				if(num < 0)
					break;
				multinomial1.combining(multinomial1.head);
				multinomial1.Print(multinomial1.head);
				System.in.read();
			}
			if(multinomial1!=null)
				multinomial1.mulcopy();
		}
		s.close();
	}
}