16.基于二分搜索树实现Map

￡神魔★判官ぃ 2022-02-28 14:38 223阅读 0赞

package com.cl.map;
    
    import com.cl.set.FileOperation;
    
    import java.util.ArrayList;
    
    public class BSTMap<K extends Comparable<K>,V> implements Map<K,V> {
    
        private class Node{
            public K key;
            public V value;
            public Node left,right;
            public Node(K key,V value){
                this.key=key;
                this.value = value;
                this.left = this.right=null;
            }
        }
    
        private Node root;
        private int size;
        public BSTMap() {
            root = null;
            size = 0;
        }
    
        private Node getNode(Node node,K key){
            if(node==null){
                return null;
            }
            if(key.compareTo(node.key)==0){
                return node;
            }else if(key.compareTo(node.key)<0){
                return getNode(node.left,key);
            }else{
                return getNode(node.right,key);
            }
        }
        @Override
        public void add(K key,V value){
            root =  add(root,key,value);
        }
    
        /**递归
         * 向以node为根节点的树插入元素
         * @return:返回插入新结点后二分搜索树的根
         */
        private Node add(Node node,K key,V value){
            if(node==null){
                size++;
                return new Node(key,value);
            }
            //递归调用
            if(key.compareTo(node.key)<0)
                node.left=add(node.left,key,value);
            else if(key.compareTo(node.key)>0){
                node.right=add(node.right,key,value);
            }else{//重新设值
                node.value=value;
            }
            return node;
        }
    
        /**
         * 找以node为根的树的最小结点
         * @param node
         * @return 返回最小的结点
         */
        private Node minmum(Node node) {
            if(node.left==null){
                return node;
            }
            return minmum(node.left);
        }
    
        /**
         * 删除以node为根节点的树的最小节点
         * @param node
         * @return：返回删除后的子树的根
         */
        private Node removeMin(Node node) {
            if(node.left==null){//找到最小值的结点
                Node rigthNode = node.right;//null或者非空
                node.right=null;
                size--;
                return rigthNode;
            }
            node.left = removeMin(node.left);
            return node;
    
        }
    
        @Override
        public V remove(K key) {
            Node node = getNode(root,key);
            if(node!=null){
                root = remove(root,key);
                return node.value;
            }
            return null;
        }
    
        private Node remove(Node node, K key) {
            //没找到
            if(node==null){
                return null;
            }
    
            if(key.compareTo(node.key)<0){
                node.left = remove(node.left,key);
                return node;
            }else if(key.compareTo(node.key)>0){
                node.right=remove(node.right,key);
                return node;
            }else {//e==node.e,找到删除的结点
                //左子树空
                if(node.left==null){
                    Node rightNoe = node.right;
                    node.right=null;
                    size--;
                    return rightNoe;
                }else if(node.right==null){//右子树空
                    Node leftNode = node.left;
                    node.left=null;
                    size--;
                    return leftNode;
                }else{//都不空
                    //找到比待删除结点的右子树中最小的结点
                    //用这个结点删除待删除的结点
                    Node successor = minmum(node.right);
                    //removeMin里有一次size--
                    successor.right = removeMin(node.right);
                    successor.left = node.left;
                    node.left=node.right=null;
                    return successor;
                }
            }
        }
    
        @Override
        public boolean contains(K key) {
            return getNode(root,key)!=null;
        }
    
        @Override
        public V get(K key) {
            Node node = getNode(root,key);
            return node == null?null:node.value;
        }
    
        @Override
        public void set(K key, V value) {
            Node node = getNode(root,key);
            if(node==null){
                throw new IllegalArgumentException(node+" not exist");
            }
            node.value=value;
        }
    
        @Override
        public int getSise() {
            return size;
        }
    
        @Override
        public boolean isEmpty() {
            return size==0;
        }
    
        public static void main(String[] args) {
            String filename = "pride-and-prejudice.txt";
            ArrayList<String> words1 = new ArrayList<>();
            FileOperation.readFile("src/"+filename,words1);
            System.out.println("Total words:"+words1.size());
            BSTMap<String,Integer> map = new BSTMap<>();
            for (String word:words1) {
                if(map.contains(word)){
                    map.set(word,map.get(word)+1);
                }
                else map.add(word,1);
            }
            System.out.println("Total diffrent words:"+map.getSise());
            System.out.println("Frenquncy of pride:"+map.get("pride"));
    
        }
    }