你將如何在此實現一棵二叉樹？

Question

如何在下面的代碼中實現二叉樹？我需要它以id的數字順序打印出下面的內容。

import java.util.Scanner; 

class clubmember { 

    public static void main(String[] args) { 

     int id; 
     String fname, lname; 
     Scanner input = new Scanner(System.in); 

     System.out.println("ID>"); 
     id = input.nextInt(); 

     System.out.println("Fname >"); 
     fname = input.next(); 

     System.out.println("lname >"); 
     lname = input.next(); 


     Person object1 = new Person(id, fname, lname); 

     System.out.println(object1); 


    } 
} 




public class Person { 
    private final int id; 
    private final String firstName; 
    private final String lastName; 


    public Person(int id, String firstName, String lastName) { 
     this.id = id; 
     this.firstName = firstName; 
     this.lastName = lastName; 
    } 

    public int getId() { 
     return id; 
    } 

    public String getFirstName() { 
     return firstName; 
    } 

    public String getLastName() { 
     return lastName; 
    } 

    @Override 
    public String toString() { 
     return String.valueOf(id) + ": " + firstName + " " + lastName; 
    } 
} 

我實際上被要求使用這棵樹作爲例子......任何人都可以幫忙嗎？

public class BinaryTreeTest { 

    public static void main(String[] args) { 
    new BinaryTreeTest().run(); 
    } 

    // Node Class 
    static class Node { 
    Node left; 

    Node right; 

    int value; 

    public Node(int value) { 
     this.value = value; 
    } 
    } 

    public void run() { 
    // build simple tree 

    Node root = new Node(5); 
    System.out.println("Binary Tree Example"); 
    System.out.println("Building tree with root value of ID " + root.value); 
    insert(root, 1); 
    insert(root, 8); 
    insert(root, 6); 
    insert(root, 3); 
    insert(root, 9); 
    System.out.println("Traversing tree in order"); 
    printInOrder(root); 
    System.out.println("Traversing tree front-to-back from location 7"); 
    printFrontToBack(root, 7); 
    } 

    public void insert(Node node, int value) { 
    if (value < node.value) { 
     if (node.left != null) { 
     insert(node.left, value); 
     } else { 
     System.out.println(" Inserted " + value + " to left of " 
      + node.value); 
     node.left = new Node(value); 
     } 
    } else if (value > node.value) { 
     if (node.right != null) { 
     insert(node.right, value); 
     } else { 
     System.out.println(" Inserted " + value + " to right of " 
      + node.value); 
     node.right = new Node(value); 
     } 
    } 
    } 

    public void printInOrder(Node node) { 
    if (node != null) { 
     printInOrder(node.left); 
     System.out.println(" Traversed " + node.value); 
     printInOrder(node.right); 
    } 
    } 

    /** 
    * uses in-order traversal when the origin is less than the node's value 
    * 
    * uses reverse-order traversal when the origin is greater than the node's 
    * order 
    */ 
    public void printFrontToBack(Node node, int idNumber) { 
    if (node == null) 
     return; 
    if (node.value > idNumber) { 
     // print in order 
     printFrontToBack(node.left, idNumber); 
     System.out.println(" Traversed " + node.value); 
     printFrontToBack(node.right, idNumber); 
    } else if (node.value < idNumber) { 
     // print reverse order 
     printFrontToBack(node.right, idNumber); 
     System.out.println(" Traversed " + node.value); 
     printFrontToBack(node.left, idNumber); 
    } else { 
     // order doesn't matter 
     printFrontToBack(node.left, idNumber); 
     printFrontToBack(node.right, idNumber); 
    } 
    } 

} 

Answer 1

如果你想保持你的對象由一個ID排序，你可以使用TreeMap。

public static void main(String[] args) { 
    Map<Integer, Person> persons = new TreeMap<Integer, Person>(); 
    persons.put(433, new Person(433, "John", "Smith"); 
    persons.put(211, new Person(211, "Peter", "Johnson"); 
    persons.put(556, new Person(556, "Laura", "Walters"); 

    // This loop will print out ordering by id 
    for (Integer key: persons.keySet()) 
     System.out.println(persons.get(key)); 
} 

Answer 2

您還可以讓Person實現Comparable，然後添加一個compareTo（Person p）方法。 然後，您可以將所有生成的Person對象添加到ArrayList，並使用Collections.sort（）對其進行排序。