Question

我需要构建一个简单的二叉树，其中包含Person元素。人员必须按身高（从低到高）排序。如果有两个人身高相同但性别不同，那么男人应该是第一位的。通常我们使用元素的左右节点。我怎样才能建造树木呢？

以下是人们的创作方式：

Person john = new Person() {
    @Override
    public boolean isMale() {
        return true;
    }
    @Override
    public int getID() {
        return 1;
    }
    @Override
    public int getHeight() {
        return 175;
    }
};

这是一个界面：

public interface Person {
    public int getID();
    public boolean isMale();
    public int getHeight();
}

Answer 1

Full code with test class

Node.java

public class Node {
    double key = 0;
    Node parent = null, left = null, right = null;
    IDancer dancer = null;
    public Node(IDancer d) {
        this.dancer = d;
        String key = d.getHeight() +  (d.isMale() ? "0." : "1.") + d.getID();
        this.key = Double.parseDouble(key);
        System.out.println("new node: " + this.key);
    }
    public void copy(double key, IDancer d) {
        this.dancer = d;
        this.key = key;
    }
    public boolean hasRight() {
        if (this.right != null) return true;
        else return false;
    }
    public boolean hasLeft() {
        if (this.left != null) return true;
        else return false;
    }
    public boolean hasParent() {
        if (this.parent != null) return true;
        else return false;
    }
    public boolean isMale() {
        if (this.dancer.isMale())
            return true;
        else return false;
    }
}

Dancers.java

import java.util.AbstractMap.SimpleEntry;
import java.util.ArrayList;
import java.util.List;
public class Dancers implements IDancers {
    public Tree tree = new Tree();
    @Override
    public SimpleEntry<IDancer, IDancer> findPartnerFor(IDancer d) throws IllegalArgumentException {
        if (!(d instanceof IDancer) ||
            (d.getHeight() <= 0) ||
            (d.getID() <= 0)) throw new IllegalArgumentException();
        IDancer partner = null;
        tree.insert(d);
        try {partner = (d.isMale()) ? tree.female(d) : tree.male(d);
        } catch (NullPointerException n) {return null;}
        if (partner != null) {
            tree.remove(d);
            tree.remove(partner);
            System.err.println("Partner: "
                    + d.getID() 
                    + (d.isMale() ? "M " : "F ") 
                    + " For: " 
                    + partner.getID() 
                    + (partner.isMale() ? "M " : "F "));
            return new SimpleEntry<IDancer, IDancer>(d, partner);
        } return null;
    }
    @Override
    public List<IDancer> returnWaitingList() {
        try {return tree.inorder(tree.root, new ArrayList<IDancer>());
        } catch(NullPointerException n) {return new ArrayList<IDancer>();}
    }
}

Tree.java

import java.util.ArrayList;
public class Tree {
    public Node root = null;
    public IDancer male(IDancer female) {
        Node current = search(genKey(female));
        Node tmp = succsessor(current);
        while (!tmp.isMale()) {
            tmp = succsessor(tmp);
        } return tmp.isMale() ? tmp.dancer : null;
    }
    public IDancer female(IDancer male) {
        Node current = search(genKey(male));
        Node tmp = predecessor(current);
        while (tmp.isMale()) {
            tmp = predecessor(tmp);
        } return  tmp.isMale() ? null : tmp.dancer;
    }
    public Node minimum() {return minimum(this.root);}
    private Node minimum(Node node) {
        if (node.hasLeft())
            return minimum(node.left);
        else return node;
    }
    public Node maximum() {return maximum(this.root);}
    public Node maximum(Node node) {
        if (node.hasRight())
            return maximum(node.right);
        else return node;
    }
    public double genKey(IDancer d) {
        return Double.parseDouble(d.getHeight() +  (d.isMale() ? "0." : "1.") + d.getID());
    }
    private Node search(double key, Node current) {
        if (current.key == key) return current;
        if (current.key > key
                && current.hasLeft())
            return search(key, current.left);
        if (current.key < key
                && current.hasRight())
            return search(key, current.right);
        return null;
    }
    public Node search(double key) {return search(key, this.root);}
    public void insert(IDancer d) {
        Node dancer = new Node(d);
        Node y = null;
        if (root == null) {
            this.root = dancer;
            return;
        }
        Node x = this.root;
        while (x != null) {
            y = x;
            if (dancer.key < x.key) x = x.left;
            else x = x.right;
        } dancer.parent = y;
        if (y == null) this.root = dancer;
        else {
            if (dancer.key < y.key) y.left = dancer;
            else y.right = dancer;
        }
    }
    public ArrayList<IDancer> inorder(Node node, ArrayList<IDancer> output) {
        if (node.hasLeft())
            inorder(node.left, output);
        output.add(node.dancer);
        if (node.hasRight())
            inorder(node.right, output);
        return output;
    }
    public void remove(IDancer d) {
        Node z = search(genKey(d)); //toRemove
        Node y = null; //replacer
        Node x = null;
        if (!z.hasLeft() || !z.hasRight()) 
            y = z;
        else y = succsessor(z);
        if (y.hasLeft())
            x = y.left;
        else x = y.right;
        if (x != null)
            x.parent = y.parent;
        if (!y.hasParent())
            this.root = x;
        else if (y == y.parent.left)
            y.parent.left = x;
        else y.parent.right = x;
        if (y != z)
            z.dancer = y.dancer;
        y = null;
    }
    private Node succsessor(Node n) {
        if (n.hasRight())
            return minimum(n.right);
        Node tmp = n.hasParent() ? n.parent : null;
        while (tmp != null && n == tmp.right) {
            n = tmp;
            tmp = tmp.parent;
        } return tmp;
    }
    private Node predecessor(Node n) {
        if (n.hasLeft())
            return maximum(n.left);
        Node tmp = n.hasParent() ? n.parent : null;
        while (tmp != null && n == tmp.left) {
            n = tmp;
            tmp = tmp.parent;
        } return tmp;
    }
}

如何从给定的接口构建二叉树

1 个答案: