Question

我遇到了二进制搜索树的问题。

我已经将文件文件读入arrayList并尝试将其放入二进制搜索树中，但是当我尝试调用bst.insert函数然后通过调用printTree进行检查时，它显示为空。任何帮助将不胜感激。

这是BST文件

import java.util.Comparator;

public class BST<AnyType extends Comparable<AnyType>>  {

    private BinaryNode<AnyType> root;

    public BST()
    {
        root = null;
    }

    public void insert (AnyType x)
    {
        root = insert(x, root);
    }

    public void remove(AnyType x)
    {
        root = remove(x, root);
    }

    public AnyType findMin()
    {
        if(isEmpty())
            throw new RuntimeException();
        return findMin(root).element;
    }

    public AnyType findMax()
    {
        if(isEmpty())
            throw new RuntimeException();
        return findMax(root).element;
    }

    public boolean contains(AnyType x)
    {
        return contains(x, root);
    }

    public boolean isEmpty()
    {
        return root == null;
    }

    public void printTree()
    {
        if (isEmpty())
            System.out.println("Tree is Empty");
        else
            printTree(root);
    }

    private BinaryNode<AnyType> insert(AnyType x, BinaryNode<AnyType> t)
    {
        if(t==null)
            return new BinaryNode<AnyType>(x,null,null);

        int compareResult = x.compareTo(t.element);

        if(compareResult < 0)
            t.left = insert(x,t.left);
        else if (compareResult > 0)
            t.right = insert(x, t.right);
        else
            ;
        return t;
    }

    private BinaryNode<AnyType> remove(AnyType x, BinaryNode<AnyType> t)
    {
        if(t==null)
            return t;

        int compareResult = x.compareTo(t.element);

        if(compareResult < 0)
            t.left = remove(x, t.left);
        else if(compareResult > 0)
            t.right = remove(x, t.right);
        else if (t.left != null && t.right != null)
        {
            t.element = findMin(t.right).element;
            t.right = remove(t.element, t.right);
        }
        else
            t = (t.left != null) ? t.left : t.right;
        return t;
    }

    private BinaryNode<AnyType> findMin (BinaryNode<AnyType> t)
    {
        if (t == null)
            return null;
        else if (t.left == null)
            return t;
        return findMin(t.left);
    }

    private BinaryNode<AnyType> findMax (BinaryNode<AnyType> t)
    {
        if (t != null)
            while(t.right != null)
                t = t.right;
        return t;
    }

    private boolean contains(AnyType x, BinaryNode<AnyType> t)
    {
        if (t == null)
            return false;

        int compareResult = x.compareTo(t.element);

        if(compareResult < 0)
            return contains(x, t.left);

        else if (compareResult > 0)
            return contains (x, t.right);
        else
            return true;
    }

    private void printTree (BinaryNode<AnyType> t)
    {
        if (t != null)
        {
            printTree(t.left);
            System.out.println(t.element);
            printTree(t.right);
        }
    }

    private int height(BinaryNode<AnyType> t)
    {
        if (t == null)
            return -1;
        else
            return 1 + Math.max(height(t.left), height(t.right));
    }

    private static class BinaryNode<AnyType>
    {
        BinaryNode(AnyType theElement)
        {
            this(theElement, null, null);
        }

        BinaryNode(AnyType theElement, BinaryNode<AnyType> lt, BinaryNode<AnyType> rt)
        {
            element = theElement;
            left = lt;
            right = rt;
        }

        AnyType element;
        BinaryNode<AnyType> left;
        BinaryNode<AnyType> right;
    }
}

主文件：

import java.io.File;
import java.io.FileNotFoundException;
import java.util.*;

public class Main {

    public static void main(String[] args) {

        Clinic c1 = new Clinic();
        BST<Patient> bst = new BST<Patient>();
        try{
            File f = new File("patients.txt");
            Scanner x = new Scanner(f);



            while(x.hasNextLine()){
                String line = x.nextLine();
                String[] detail = line.split("\t",4);
                String name = detail[0];
                String doctor = detail[1];
                String currApp = detail[2];
                String nextApp = detail[3];
                Patient p = new Patient(name, doctor, currApp, nextApp);
                c1.addPatient(p);
                c1.assignDoctor();
            }
        } catch (FileNotFoundException e){
            e.printStackTrace();
        }

        //sort ArrayList of patients
        Collections.sort(c1.patientList, new Comparator<Patient>(){
            @Override
            public int compare(Patient o1, Patient o2){
                return o1.getName().compareTo(o2.getName());
            }
        });
        List<Patient> list = new ArrayList<Patient>();

        for (Patient p: list){
            bst.insert(p);
        }
        bst.printTree();
    }
}

患者档案：

public class Patient implements Comparable<Patient>{
    private String patientName;
    private String doctorName;
    private String  currAppt;
    private String nextAppt;

    Patient (String patientName,String doctorName ,String currAppt, String    nextAppt)
    {
        this.patientName= patientName;
        this.doctorName = doctorName;
        this.currAppt = currAppt;
        this.nextAppt= nextAppt;
    }   

    public String getDoctor()
    {return doctorName;}

    public String getName()
    {
        return patientName;
    }

    public String toString()
    {
        return (patientName+" "+doctorName+" "+currAppt +" "+ nextAppt);
    }

    @Override
    public int compareTo(Patient o) {
        if (patientName.equals(o))
        return 0;
        return patientName.compareTo(o.patientName);
    }
}

Answer 1

问题在于这一部分：

List<Patient> list = new ArrayList<Patient>();

for (Patient p: list){
    bst.insert(p);
}

将列表初始化为空数组列表，然后遍历空列表并添加任何患者。由于它是空的，因此该循环从不向BST添加任何内容。我猜你实际上是想在那里使用c1.patientList。所以：

List<Patient> list = new ArrayList<Patient>();

for (Patient p: c1.patientList){
    bst.insert(p);
}

从ArrayList插入BST将不起作用

1 个答案: