java实现数据结构13（红黑树详解代码之自定义红黑树）

布满荆棘的人生 2023-06-25 02:15 61阅读 0赞

## 自定义红黑树 ##

import com.sun.org.apache.regexp.internal.RE;
    
    /** * @description: 自定义红黑树 * @author: liangrui * @create: 2019-12-24 13:50 **/
    public class RedBlackTree<K extends Comparable<K>,V> { 
    
        private static final boolean RED=true;
        private static final boolean BLACK=false;
    
        private class Node{ 
            public K key;
            public V value;
            public Node left,right;
            public boolean color;
    
            public Node(K key,V value){ 
                this.key=key;
                this.value=value;
                left=null;
                right=null;
                color=RED;
            }
        }
    
        private Node root;
        private int size;
    
        public RedBlackTree(){ 
            root=null;
            size=0;
        }
    
        public int getSize(){ 
            return size;
        }
    
        public boolean isEmpty(){ 
            return size==0;
        }
    
        /** * 判断节点node的颜色 * @param node * @return */
        private boolean isRed(Node node){ 
            if (node==null){ 
                return BLACK;
            }
            return node.color;
        }
    
        // node x
        // / \ 左旋转 / \
        // T1 x ---------> node T3
        // / \ / \
        // T2 T3 T1 T2
        private Node leftRotate(Node node){ 
            Node x=node.right;
    
            //左旋转
            node.right=x.left;
            x.left=node;
    
            x.color=node.color;
            node.color=RED;
    
            return x;
        }
    
        // node x
        // / \ 右旋转 / \
        // x T2 -------> y node
        // / \ / \
        // y T1 T1 T2
        private Node rightRotate(Node node){ 
            Node x=node.left;
    
            //右旋转
            node.left=x.right;
            x.right=node;
    
            x.color=node.color;
            node.color=RED;
    
            return x;
        }
    
        /** * 颜色翻转 * @param node */
        private void flipColors(Node node){ 
            node.color=RED;
            node.left.color=BLACK;
            node.right.color=BLACK;
        }
    
        /** * 向红黑树中添加新的元素(key,value) * @param key * @param value */
        public void add(K key,V value){ 
            root=add(root,key,value);
            root.color=BLACK;
        }
    
        /** * 向以node为根的红黑树中插入元素(key,value),递归算法 * @param node * @param key * @param value * @return 返回插入新节点后红黑树的根 */
        private Node add(Node node, K key, V value) { 
            if (node==null){ 
                size++;
                return new Node(key, value);//默认插入红色节点
            }
    
            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 { 
                node.value=value;
            }
    
            if (isRed(node.right)&&!isRed(node.left)){ 
                node=leftRotate(node);
            }
    
            if (isRed(node.left)&&isRed(node.left.left)){ 
                node=rightRotate(node);
            }
    
            if (isRed(node.left)&&isRed(node.right)){ 
                flipColors(node);
            }
    
            return node;
        }
    
        // 返回以node为根节点的二分搜索树中，key所在的节点
        private Node getNode(Node node, K key){ 
    
            if(node == null)
                return null;
    
            if(key.equals(node.key))
                return node;
            else if(key.compareTo(node.key) < 0)
                return getNode(node.left, key);
            else // if(key.compareTo(node.key) > 0)
                return getNode(node.right, key);
        }
    
        public boolean contains(K key){ 
            return getNode(root, key) != null;
        }
    
        public V get(K key){ 
    
            Node node = getNode(root, key);
            return node == null ? null : node.value;
        }
    
        public void set(K key, V newValue){ 
            Node node = getNode(root, key);
            if(node == null)
                throw new IllegalArgumentException(key + " doesn't exist!");
    
            node.value = newValue;
        }
    }

## main测试 ##

import java.util.ArrayList;
    
    public class Main { 
    
        public static void main(String[] args) { 
            System.out.println("Pride and Prejudice");
    
            ArrayList<String> words=new ArrayList<>();
            if (FileOperation.readFile("pride-and-prejudice.txt",words)){ 
                System.out.println("Total words:"+words.size());
    
                RedBlackTree<String,Integer> redBlackTree=new RedBlackTree<>();
                for (String word : words) { 
                    if (redBlackTree.contains(word)){ 
                        redBlackTree.set(word,redBlackTree.get(word)+1);
                    }else { 
                        redBlackTree.add(word,1);
                    }
                }
    
                System.out.println("Total different words:"+redBlackTree.getSize());
                System.out.println("Frequency of 'pride':"+redBlackTree.get("pride"));
                System.out.println("Frequency of 'prejudice':"+redBlackTree.get("prejudice"));
            }
        }
    }

## 文件操作类FileOperation ##

import java.io.BufferedInputStream;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.Locale;
    import java.util.Scanner;
    
    // 文件相关操作
    public class FileOperation { 
    
        // 读取文件名称为filename中的内容，并将其中包含的所有词语放进words中
        public static boolean readFile(String filename, ArrayList<String> words){ 
    
            if (filename == null || words == null){ 
                System.out.println("filename is null or words is null");
                return false;
            }
    
            // 文件读取
            Scanner scanner;
    
            try { 
                File file = new File(filename);
                if(file.exists()){ 
                    FileInputStream fis = new FileInputStream(file);
                    scanner = new Scanner(new BufferedInputStream(fis), "UTF-8");
                    scanner.useLocale(Locale.ENGLISH);
                }
                else
                    return false;
            }
            catch(IOException ioe){ 
                System.out.println("Cannot open " + filename);
                return false;
            }
    
            // 简单分词
            // 这个分词方式相对简陋, 没有考虑很多文本处理中的特殊问题
            // 在这里只做demo展示用
            if (scanner.hasNextLine()) { 
    
                String contents = scanner.useDelimiter("\\A").next();
    
                int start = firstCharacterIndex(contents, 0);
                for (int i = start + 1; i <= contents.length(); )
                    if (i == contents.length() || !Character.isLetter(contents.charAt(i))) { 
                        String word = contents.substring(start, i).toLowerCase();
                        words.add(word);
                        start = firstCharacterIndex(contents, i);
                        i = start + 1;
                    } else
                        i++;
            }
    
            return true;
        }
    
        // 寻找字符串s中，从start的位置开始的第一个字母字符的位置
        private static int firstCharacterIndex(String s, int start){ 
    
            for( int i = start ; i < s.length() ; i ++ )
                if( Character.isLetter(s.charAt(i)) )
                    return i;
            return s.length();
        }
    }

## 测试结果： ##

> Pride and Prejudice  
> Total words:125901  
> Total different words:6530  
> Frequency of ‘pride’:53  
> Frequency of ‘prejudice’:11

## pride-and-prejudice.txt文件（傲慢与偏见）随便一个txt文件都可以测试（必须为英文） ##