映射01--第11天

Posted 2021-03-09 ggnbnb

1.映射

1.1基本概念

 

 1.2接口设计

 

 1.3Map与Set区别

 

 2.相关代码

Map

public interface Map<K, V> {
    int size();
    boolean isEmpty();
    void clear();
    V put(K key, V value);
    V get(K key);
    V remove(K key);
    boolean containsKey(K key);
    boolean containsValue(V value);
    void traversal(Visitor<K, V> visitor);
    
    public static abstract class Visitor<K, V> {
        boolean stop;
        public abstract boolean visit(K key, V value);
    }
}

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TreeMap

import java.util.Comparator;
import java.util.LinkedList;
import java.util.Queue;

@SuppressWarnings({"unchecked", "unused"})
public class TreeMap<K, V> implements Map<K, V> {
    private static final boolean RED = false;
    private static final boolean BLACK = true;
    private int size;
    private Node<K, V> root;
    private Comparator<K> comparator;
    
    public TreeMap() {
        this(null);
    }
    
    public TreeMap(Comparator<K> comparator) {
        this.comparator = comparator;
    }
    
    public int size() {
        return size;
    }

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

    public void clear() {
        root = null;
        size = 0;
    }

    @Override
    public V put(K key, V value) {
        keyNotNullCheck(key);
        
        // 添加第一个节点
        if (root == null) {
            root = new Node<>(key, value, null);
            size++;

            // 新添加节点之后的处理
            afterPut(root);
            return null;
        }
        
        // 添加的不是第一个节点
        // 找到父节点
        Node<K, V> parent = root;
        Node<K, V> node = root;
        int cmp = 0;
        do {
            cmp = compare(key, node.key);
            parent = node;
            if (cmp > 0) {
                node = node.right;
            } else if (cmp < 0) {
                node = node.left;
            } else { // 相等
                node.key = key;
                V oldValue = node.value;
                node.value = value;
                return oldValue;
            }
        } while (node != null);

        // 看看插入到父节点的哪个位置
        Node<K, V> newNode = new Node<>(key, value, parent);
        if (cmp > 0) {
            parent.right = newNode;
        } else {
            parent.left = newNode;
        }
        size++;
        
        // 新添加节点之后的处理
        afterPut(newNode);
        return null;
    }

    @Override
    public V get(K key) {
        Node<K, V> node = node(key);
        return node != null ? node.value : null;
    }

    @Override
    public V remove(K key) {
        return remove(node(key));
    }

    @Override
    public boolean containsKey(K key) {
        return node(key) != null;
    }

    @Override
    public boolean containsValue(V value) {
        if (root == null) return false;
        
        Queue<Node<K, V>> queue = new LinkedList<>();
        queue.offer(root);
        
        while (!queue.isEmpty()) {
            Node<K, V> node = queue.poll();
            if (valEquals(value, node.value)) return true;
            
            if (node.left != null) {
                queue.offer(node.left);
            }
            
            if (node.right != null) {
                queue.offer(node.right);
            }
        }
        
        return false;
    }

    @Override
    public void traversal(Visitor<K, V> visitor) {
        if (visitor == null) return;
        traversal(root, visitor);
    }
    
    private void traversal(Node<K, V> node, Visitor<K, V> visitor) {
        if (node == null || visitor.stop) return;
        
        traversal(node.left, visitor);
        if (visitor.stop) return;
        visitor.visit(node.key, node.value);
        traversal(node.right, visitor);
    }
    
    private boolean valEquals(V v1, V v2) {
        return v1 == null ? v2 == null : v1.equals(v2);
    }
    
    private V remove(Node<K, V> node) {
        if (node == null) return null;
        
        size--;
        
        V oldValue = node.value;
        
        if (node.hasTwoChildren()) { // 度为2的节点
            // 找到后继节点
            Node<K, V> s = successor(node);
            // 用后继节点的值覆盖度为2的节点的值
            node.key = s.key;
            node.value = s.value;
            // 删除后继节点
            node = s;
        }
        
        // 删除node节点（node的度必然是1或者0）
        Node<K, V> replacement = node.left != null ? node.left : node.right;
        
        if (replacement != null) { // node是度为1的节点
            // 更改parent
            replacement.parent = node.parent;
            // 更改parent的left、right的指向
            if (node.parent == null) { // node是度为1的节点并且是根节点
                root = replacement;
            } else if (node == node.parent.left) {
                node.parent.left = replacement;
            } else { // node == node.parent.right
                node.parent.right = replacement;
            }
            
            // 删除节点之后的处理
            afterRemove(replacement);
        } else if (node.parent == null) { // node是叶子节点并且是根节点
            root = null;
        } else { // node是叶子节点，但不是根节点
            if (node == node.parent.left) {
                node.parent.left = null;
            } else { // node == node.parent.right
                node.parent.right = null;
            }
            
            // 删除节点之后的处理
            afterRemove(node);
        }
        
        return oldValue;
    }
    
    private void afterRemove(Node<K, V> node) {
        // 如果删除的节点是红色
        // 或者 用以取代删除节点的子节点是红色
        if (isRed(node)) {
            black(node);
            return;
        }
        
        Node<K, V> parent = node.parent;
        if (parent == null) return;
        
        // 删除的是黑色叶子节点【下溢】
        // 判断被删除的node是左还是右
        boolean left = parent.left == null || node.isLeftChild();
        Node<K, V> sibling = left ? parent.right : parent.left;
        if (left) { // 被删除的节点在左边，兄弟节点在右边
            if (isRed(sibling)) { // 兄弟节点是红色
                black(sibling);
                red(parent);
                rotateLeft(parent);
                // 更换兄弟
                sibling = parent.right;
            }
            
            // 兄弟节点必然是黑色
            if (isBlack(sibling.left) && isBlack(sibling.right)) {
                // 兄弟节点没有1个红色子节点，父节点要向下跟兄弟节点合并
                boolean parentBlack = isBlack(parent);
                black(parent);
                red(sibling);
                if (parentBlack) {
                    afterRemove(parent);
                }
            } else { // 兄弟节点至少有1个红色子节点，向兄弟节点借元素
                // 兄弟节点的左边是黑色，兄弟要先旋转
                if (isBlack(sibling.right)) {
                    rotateRight(sibling);
                    sibling = parent.right;
                }
                
                color(sibling, colorOf(parent));
                black(sibling.right);
                black(parent);
                rotateLeft(parent);
            }
        } else { // 被删除的节点在右边，兄弟节点在左边
            if (isRed(sibling)) { // 兄弟节点是红色
                black(sibling);
                red(parent);
                rotateRight(parent);
                // 更换兄弟
                sibling = parent.left;
            }
            
            // 兄弟节点必然是黑色
            if (isBlack(sibling.left) && isBlack(sibling.right)) {
                // 兄弟节点没有1个红色子节点，父节点要向下跟兄弟节点合并
                boolean parentBlack = isBlack(parent);
                black(parent);
                red(sibling);
                if (parentBlack) {
                    afterRemove(parent);
                }
            } else { // 兄弟节点至少有1个红色子节点，向兄弟节点借元素
                // 兄弟节点的左边是黑色，兄弟要先旋转
                if (isBlack(sibling.left)) {
                    rotateLeft(sibling);
                    sibling = parent.left;
                }
                
                color(sibling, colorOf(parent));
                black(sibling.left);
                black(parent);
                rotateRight(parent);
            }
        }
    }

    private Node<K, V> predecessor(Node<K, V> node) {
        if (node == null) return null;
        
        // 前驱节点在左子树当中（left.right.right.right....）
        Node<K, V> p = node.left;
        if (p != null) {
            while (p.right != null) {
                p = p.right;
            }
            return p;
        }
        
        // 从父节点、祖父节点中寻找前驱节点
        while (node.parent != null && node == node.parent.left) {
            node = node.parent;
        }

        // node.parent == null
        // node == node.parent.right
        return node.parent;
    }
    
    private Node<K, V> successor(Node<K, V> node) {
        if (node == null) return null;
        
        // 前驱节点在左子树当中（right.left.left.left....）
        Node<K, V> p = node.right;
        if (p != null) {
            while (p.left != null) {
                p = p.left;
            }
            return p;
        }
        
        // 从父节点、祖父节点中寻找前驱节点
        while (node.parent != null && node == node.parent.right) {
            node = node.parent;
        }

        return node.parent;
    }
    
    private Node<K, V> node(K key) {
        Node<K, V> node = root;
        while (node != null) {
            int cmp = compare(key, node.key);
            if (cmp == 0) return node;
            if (cmp > 0) {
                node = node.right;
            } else { // cmp < 0
                node = node.left;
            }
        }
        return null;
    }
    
    private void afterPut(Node<K, V> node) {
        Node<K, V> parent = node.parent;
        
        // 添加的是根节点 或者 上溢到达了根节点
        if (parent == null) {
            black(node);
            return;
        }
        
        // 如果父节点是黑色，直接返回
        if (isBlack(parent)) return;
        
        // 叔父节点
        Node<K, V> uncle = parent.sibling();
        // 祖父节点
        Node<K, V> grand = red(parent.parent);
        if (isRed(uncle)) { // 叔父节点是红色【B树节点上溢】
            black(parent);
            black(uncle);
            // 把祖父节点当做是新添加的节点
            afterPut(grand);
            return;
        }
        
        // 叔父节点不是红色
        if (parent.isLeftChild()) { // L
            if (node.isLeftChild()) { // LL
                black(parent);
            } else { // LR
                black(node);
                rotateLeft(parent);
            }
            rotateRight(grand);
        } else { // R
            if (node.isLeftChild()) { // RL
                black(node);
                rotateRight(parent);
            } else { // RR
                black(parent);
            }
            rotateLeft(grand);
        }
    }
    
    private void rotateLeft(Node<K, V> grand) {
        Node<K, V> parent = grand.right;
        Node<K, V> child = parent.left;
        grand.right = child;
        parent.left = grand;
        afterRotate(grand, parent, child);
    }
    
    private void rotateRight(Node<K, V> grand) {
        Node<K, V> parent = grand.left;
        Node<K, V> child = parent.right;
        grand.left = child;
        parent.right = grand;
        afterRotate(grand, parent, child);
    }
    
    private void afterRotate(Node<K, V> grand, Node<K, V> parent, Node<K, V> child) {
        // 让parent称为子树的根节点
        parent.parent = grand.parent;
        if (grand.isLeftChild()) {
            grand.parent.left = parent;
        } else if (grand.isRightChild()) {
            grand.parent.right = parent;
        } else { // grand是root节点
            root = parent;
        }
        
        // 更新child的parent
        if (child != null) {
            child.parent = grand;
        }
        
        // 更新grand的parent
        grand.parent = parent;
    }

    private Node<K, V> color(Node<K, V> node, boolean color) {
        if (node == null) return node;
        node.color = color;
        return node;
    }
    
    private Node<K, V> red(Node<K, V> node) {
        return color(node, RED);
    }
    
    private Node<K, V> black(Node<K, V> node) {
        return color(node, BLACK);
    }
    
    private boolean colorOf(Node<K, V> node) {
        return node == null ? BLACK : node.color;
    }
    
    private boolean isBlack(Node<K, V> node) {
        return colorOf(node) == BLACK;
    }
    
    private boolean isRed(Node<K, V> node) {
        return colorOf(node) == RED;
    }
    
    private int compare(K e1, K e2) {
        if (comparator != null) {
            return comparator.compare(e1, e2);
        }
        return ((Comparable<K>)e1).compareTo(e2);
    }
    
    private void keyNotNullCheck(K key) {
        if (key == null) {
            throw new IllegalArgumentException("key must not be null");
        }
    }

    private static class Node<K, V> {
        K key;
        V value;
        boolean color = RED;
        Node<K, V> left;
        Node<K, V> right;
        Node<K, V> parent;
        public Node(K key, V value, Node<K, V> parent) {
            this.key = key;
            this.value = value;
            this.parent = parent;
        }
        
        public boolean isLeaf() {
            return left == null && right == null;
        }
        
        public boolean hasTwoChildren() {
            return left != null && right != null;
        }
        
        public boolean isLeftChild() {
            return parent != null && this == parent.left;
        }
        
        public boolean isRightChild() {
            return parent != null && this == parent.right;
        }
        
        public Node<K, V> sibling() {
            if (isLeftChild()) {
                return parent.right;
            }
            
            if (isRightChild()) {
                return parent.left;
            }
            
            return null;
        }
    }
}

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