集合和映射（1）—— 基于二分搜索树和基于链表实现集合

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1 基于二分搜索树的集合实现

• BST.java

package tree;


import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

/*
 *
 * 实现的二分搜索树不包含重复元素
 *
 * 如果想包含重复元素，只需要定义：
 * 左子树小于等于节点，或者右子树大于等于节点
 * */
public class BST<E extends Comparable<E>> {

    private class Node {
        public E e;
        public Node left, right;

        public Node(E e) {
            this.e = e;
            this.left = null;
            this.right = null;
        }
    }

    private Node root;
    private int size;

    public BST() {
        root = null;
        size = 0;
    }

    public int size() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    /*
     * 向二分搜索树添加新的元素
     *
     * 对应原版的 add
     * */
//    public void add(E e) {
//        if (root == null) {
//            root = new Node(e);
//            size++;
//        } else {
//            add(root, e);
//        }
//    }

    // 向以 node 为根的二分搜索树中插入元素 e,递归算法
    // 原版，比较臃肿
//    private void add(Node node, E e) {
//        if (e.equals(node.e)) {
//            return;
//        } else if (e.compareTo(node.e) < 0 && node.left == null) {
//            node.left = new Node(e);
//            size++;
//            return;
//        } else if (e.compareTo(node.e) > 0 && node.right == null) {
//            node.right = new Node(e);
//            size++;
//            return;
//        }
//
//        if (e.compareTo(node.e) < 0) {
//            add(node.left, e);
//        } else {
//            add(node.right, e);
//        }
//
//
//    }


    /*
     * 改进版添加新的元素 e
     * */
    public void add(E e) {

        root = add(root, e);
    }


    /*
     * 改进原版添加函数
     *
     * 返回插入新节点后二分搜索树的根
     *
     * */
    private Node add(Node node, E e) {
        if (node == null) {
            size++;
            return new Node(e);
        }

        if (e.compareTo(node.e) < 0) {
            node.left = add(node.left, e);
        } else if (e.compareTo(node.e) > 0) {
            node.right = add(node.right, e);
        }

        return node;

    }

    /*
     * 看二分搜索树中是否包含元素 e
     *
     * */

    public boolean contains(E e) {
        return contains(root, e);
    }


    // 查看以 node 为根的二分搜索树中是否包含元素 e, 递归算法
    private boolean contains(Node node, E e) {

        if (node == null) {
            return false;
        }

        if (e.compareTo(node.e) == 0) {
            return true;
        }

        if (e.compareTo(node.e) < 0) {
            return contains(node.left, e);
        } else {
            return contains(node.right, e);
        }
    }

    /*
     * 前序遍历
     *
     * */
    public void preOrder() {
        preOrder(root);
    }

    private void preOrder(Node node) {

        if (node == null) {
            return;
        }

        System.out.println(node.e);

        preOrder(node.left);
        preOrder(node.right);

    }


    public void preOrderNR() {

        Stack<Node> stack = new Stack<>();
        stack.push(root);
        while (!stack.isEmpty()) {
            Node cur = stack.pop();
            System.out.println(cur.e);

            if (cur.right != null) {
                stack.push(cur.right);
            }

            if (cur.left != null) {
                stack.push(cur.left);
            }

        }

    }


    /*
     * 中序遍历
     *
     * */
    public void inOrder() {
        inOrder(root);
    }

    private void inOrder(Node node) {

        if (node == null) {
            return;
        }

        inOrder(node.left);
        System.out.println(node.e);

        inOrder(node.right);

    }

    public void postOrder() {
        postOrder(root);
    }

    private void postOrder(Node node) {

        if (node == null) {
            return;
        }

        postOrder(node.left);
        postOrder(node.right);
        System.out.println(node.e);
    }


    public void levelOrder() {

        Queue<Node> q = new LinkedList<Node>();
        q.add(root);

        while (!q.isEmpty()) {
            Node cur = q.remove();
            System.out.println(cur.e);

            if (cur.left != null) {
                q.add(cur.left);
            }
            if (cur.right != null) {
                q.add(cur.right);
            }
        }
    }


    public E minimum() {
        if (size == 0) {
            throw new IllegalArgumentException("BST is empty");
        }

        return minimum(root).e;
    }

    //返回以 node 为根的二分搜索树的最小值的节点
    private Node minimum(Node node) {

        if (node.left == null) {
            return node;
        }

        return minimum(node.left);
    }

    public E maximum() {
        if (size == 0) {
            throw new IllegalArgumentException("BST is empty");

        }

        return maximum(root).e;
    }

    private Node maximum(Node node) {
        if (node.right == null) {
            return node;
        }

        return maximum(node.right);
    }


    public E removeMin() {

        E ret = minimum();
        root = removeMin(root);
        return ret;
    }

    /*
     * 删除以 node 为根的二分搜索树的最小节点
     * 返回删除节点后新的二分搜索树的根
     *
     * */
    private Node removeMin(Node node) {

        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }

        node.left = removeMin(node.left);

        return node;
    }


    public E removeMax() {
        E ret = maximum();
        root = removeMax(root);
        return ret;
    }

    //删除以 node 为根的二分搜索树的最大节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMax(Node node) {
        if (node.right == null) {
            Node leftNode = node.left;
            node.left = null;
            size--;
            return leftNode;
        }

        node.right = removeMax(node.right);

        return node;
    }


    public void remove(E e) {
        root = remove(root, e);
    }

    private Node remove(Node node, E e) {

        if (node == null) {
            return null;
        }

        if (e.compareTo(node.e) < 0) {
            node.left = remove(node.left, e);
        }

        if (e.compareTo(node.e) > 0) {
            node.right = remove(node.right, e);
        } else { // e == node.e

            // 待删除节点左子树为空
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }

            if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                return leftNode;
            }

            // 待删除的节点左右子树均不为空
            // 找到比待删除节点大的最小节点，即待删除节点右子树的最小节点
            // 用这个节点顶替待删除节点的位置
            Node successor = minimum(node.right);
            successor.right = removeMin(node.right);
            successor.left = node.left;

            node.left = node.right = null;

            return successor;

        }

        return null;

    }


    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();

        generateBSTString(root, 0, res);

        return res.toString();
    }

    //生成以 node 为根节点，深度为 depth 的描述二叉树的字符串
    private void generateBSTString(Node node, int depth, StringBuilder res) {

        if (node == null) {
            res.append(generateDepthString(depth) + "null\n");
            return;
        }

        res.append(generateDepthString(depth) + node.e + "\n");

        generateBSTString(node.left, depth + 1, res);
        generateBSTString(node.right, depth + 1, res);
    }

    private String generateDepthString(int depth) {
        StringBuilder res = new StringBuilder();
        for (int i = 0; i < depth; i++) {
            res.append("--");
        }

        return res.toString();
    }
}

• Set.java

package setAndmap;

public interface Set<E> {

    void add(E e);
    void remove(E e);
    boolean contains(E e);
    int getSize();
    boolean isEmpty();
}

• BSTSet.java

package setAndmap;

import tree.BST;

public class BSTSet<E extends Comparable<E>> implements Set<E> {

    private BST<E> bst;

    public BSTSet() {
        bst = new BST<E>();
    }

    @Override
    public void add(E e) {
        bst.add(e);
    }

    @Override
    public void remove(E e) {
        bst.remove(e);
    }

    @Override
    public boolean contains(E e) {
        return bst.contains(e);
    }

    @Override
    public int getSize() {
        return bst.size();
    }

    @Override
    public boolean isEmpty() {
        return bst.isEmpty();
    }
}

2 基于链表实现集合

• LinkedList.java

package linkedlist;

public class LinkedList<E> {

    private class Node {
        public E e;
        public Node next;

        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e) {
            this(e, null);
        }

        public Node() {
            this(null, null);
        }

        @Override
        public String toString() {
            return e.toString();
        }
    }

    private Node dummyHead;
    private int size;

    public LinkedList() {
        dummyHead = new Node(null, null);
        size = 0;
    }

    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }


    /*
     * 在链表的 index (从 0 开始) 位置添加新的元素 e
     *
     * */
    public void add(int index, E e) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("add failed");
        }

        Node prev = dummyHead;
        for (int i = 0; i < index; i++) {
            prev = prev.next;
        }

//            Node node = new Node(e);
//            node.next = prev.next;
//            prev.next = node;
        prev.next = new Node(e, prev.next); // 代替上边3行

        size++;

    }

    //在链表头部添加元素
    public void addFirst(E e) {
        add(0, e);
    }


    public void addLast(E e) {
        add(size, e);
    }

    // 获得链表第 index 个元素
    public E get(int index) {

        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("add failed");
        }

        Node cur = dummyHead.next;

        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }

        return cur.e;
    }

    public E getFirst() {
        return get(0);
    }

    public E getLast() {
        return get(size - 1);
    }

    public void set(int index, E e) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("add failed");
        }

        Node cur = dummyHead.next;

        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        cur.e = e;

    }

    /*
     * 查找链表中是否存在 e
     * */
    public boolean contains(E e) {
        Node cur = dummyHead.next;

        while (cur != null) {
            if (cur.e.equals(e)) {
                return true;
            }
            cur = cur.next;
        }

        return false;
    }

    public E remove(int index) {

        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("add failed");
        }

        Node prev = dummyHead;
        for (int i = 0; i < index; i++) {
            prev = prev.next;
        }

        Node retNode = prev.next;
        prev.next = retNode.next;
        retNode.next = null;
        size--;
        return retNode.e;

    }

    //删除第一个元素
    public E removeFirst() {
        return remove(0);
    }

    public E removeLast() {
        return remove(size - 1);
    }


    // 从链表中删除元素 e
    public void removeElement(E e) {
        Node prev = dummyHead;

        while (prev.next != null) {
            if (prev.next.e.equals(e)) {
                break;
            }
            prev = prev.next;
        }

        if (prev.next != null) {
            Node delNode = prev.next;
            prev.next = delNode.next;
            delNode.next = null;
        }
    }

    @Override
    public String toString() {

        StringBuilder res = new StringBuilder();

        Node cur = dummyHead.next;
        while (cur != null) {
            res.append(cur + "->");
            cur = cur.next;
        }
        res.append("NULL");

        return res.toString();
    }
}

• LinkedListSet.java

package setAndmap;

import linkedlist.LinkedList;

public class LinkedListSet<E> implements Set<E> {

    private LinkedList<E> list;

    public LinkedListSet() {
        list = new LinkedList<>();
    }

    @Override
    public void add(E e) {
        if (!list.contains(e)) {
            list.addFirst(e);
        }
    }

    @Override
    public void remove(E e) {
        list.removeElement(e);
    }

    @Override
    public boolean contains(E e) {
        return list.contains(e);
    }

    @Override
    public int getSize() {
        return list.getSize();
    }

    @Override
    public boolean isEmpty() {
        return list.isEmpty();
    }
}