javase二叉树作业备份

import java.util.Scanner;

class BinTree {
    char data;
    BinTree L,R;
    BinTree(char x){
        data=x;
    }
    static BinTree create(ReadChar r){
        char x=r.getChar();
        if(x=='#'){
            return null;
        }
        BinTree t=new BinTree(x);
        t.L=create(r);
        t.R=create(r);
        return t;
    }
    void pre(){
        System.out.println(this.data+" ");
        if(this.L!=null)
            this.L.pre();
        if(this.R!=null)
            this.R.pre();
    }
    void in(){

        if(this.L!=null)
            this.L.in();
        System.out.println(this.data+" ");
        if(this.R!=null)
            this.R.in();
    }
    void post(){

        if(this.L!=null)
            this.L.post();
        if(this.R!=null)
            this.R.post();
        System.out.println(this.data+" ");
    }
    class Stack {
        int top;
        BinTree[] s=new BinTree[20];
        boolean isEmpty(){
            return top==0;
        }
        void push(BinTree x){
            if(top==s.length){
                BinTree[] news=new BinTree[s.length+20];
                for(int i=0;i<s.length;i++){
                    news[i]=s[i];
                    s=news;
                }
            }
            s[top]=x;
            top++;
        }
        BinTree pop(){
            top--;
            return s[top];
        }
    }
    void preN(){
        BinTree t=this;
        Stack st=new Stack();
        while(t!=null||st.isEmpty()==false){
            if(t!=null){
                System.out.println(t.data+" ");
                st.push(t);
                t=t.L;
            }
            else{
                t=st.pop();
                t=t.R;
            }
        }
    }
    void inN(){
        BinTree t=this;
        Stack st=new Stack();
        while(t!=null||st.isEmpty()==false){
            if(t!=null){

                st.push(t);
                t=t.L;
            }
            else{
                t=st.pop();
                System.out.println(t.data+" ");
                t=t.R;
            }
        }
    }
}
class ReadChar {
    String data;
    int i=0;
    ReadChar(String d){
        data=d;
    }
    char getChar(){
        char x=data.charAt(i);
        i++;
        return x;
    }
}
class App {
    public static void main(String[] args) {
        System.out.println("请输入建树数据,#表示null:");
        //AB#D##CE##F##
        Scanner sc = new Scanner(System.in);
        String str=sc.next();
        ReadChar r=new ReadChar(str);
        BinTree t=BinTree.create(r);
        System.out.println("pre=");
        t.pre();
        System.out.println("preN=");
        t.preN();
        System.out.println("in=");
        t.in();
        System.out.println("inN=");
        t.inN();
        System.out.println("post=");
        t.post();

    }
}