二叉查找樹 循環非遞歸實作

#ifndef __BINARY_SEARCH_H__
#define __BINARY_SEARCH_H__

#include <assert.h>
#include <iostream>

template <typename Key, typename Value>
class BinarySearchTree;

template <typename Key, typename Value>
std::ostream& operator<<(std::ostream &out, BinarySearchTree<Key, Value>&);

template <typename Key, typename Value>
class BinarySearchTree {
    friend std::ostream& operator<< <Key, Value>(std::ostream &out, BinarySearchTree<Key, Value> &tree);

    struct Node {
        Key key;
        Value val;
        Node *left;
        Node *right;    
        Node(Key pkey, Value pval):key(pkey), val(pval), left(nullptr), right(nullptr) {}
    };
    Node *root;

    void traverse(Node *node, std::ostream &out) {
        if (node == nullptr)
            return;
        traverse(node->left, out);
        out << "(" << node->key << ", " << node->val << ") ";
        traverse(node->right, out);
    }
public:
    BinarySearchTree(Key pkey, Value pval) :root(new Node(pkey, pval)) {}

    void put(Key key, Value val) {
        Node **node = &root;
        while (*node != nullptr)
        {
            if (key < (*node)->key)
                node = &((*node)->left);
            else if (key > (*node)->key)
                node = &((*node)->right);
            else
                return;
        }
        if(*node == nullptr)
            *node = new Node(key, val);
    }

    Value get(Key key) {
        Node *node = root;
        while (node != nullptr)
        {
            if (key < node->key)
                node = node->left;
            else if (key > node->key)
                node = node->right;
            else
                return node->val;
        }
        assert(false);
    }

    Node* deleteMin(Node* head) {
        if (head == nullptr)
            return nullptr;
        Node *node = head;
        Node *lastNode = nullptr;
        while (node->left != nullptr)
        {
            lastNode = node;
            node = node->left;    
        }
        lastNode->left = node->right;
        //delete node;
        return head;
    }

    Node* min(Node *head) {
        if (head == nullptr)
            return nullptr;
        Node *node = head;
        while (node->left != nullptr)
            node = node->left;
        return node;
    }

    void deleteNode(Key key) {
        Node *lastNode = nullptr;        
        Node *node = root;
        Node *newNode = nullptr;
        while (node != nullptr)
        {
            if (key < node->key) {
                lastNode = node;
                node = node->left;        
            }
            else if (key > node->key) {
                lastNode = node;
                node = node->right;
            }
            else {
                Node **plastNode = nullptr;
                // 注意樹根
                if (lastNode == nullptr)
                    plastNode = &root;
                else
                    plastNode = &lastNode;
                // 無節點的情況
                if (node->left == nullptr && node->right == nullptr)
                {
                    if ((*plastNode)->left == node)
                    {
                        (*plastNode)->left = nullptr;
                        delete node;
                        return;
                    }
                    else if ((*plastNode)->right == node)
                    {
                        (*plastNode)->right = nullptr;
                        delete node;
                        return;
                    }
                }
                // 隻有一個節點的情況
                if (node->left == nullptr) {
                    if ((*plastNode)->left == node) {
                        (*plastNode)->left = node->right;
                        delete node;
                        return;
                    }
                    else if ((*plastNode)->right == node) {
                        (*plastNode)->right = node->right;
                        delete node;
                        return;
                    }
                }
                if (node->right == nullptr) {
                    if ((*plastNode)->right == node) {
                        (*plastNode)->right = node->left;
                        delete node;
                        return;
                    }
                    else if ((*plastNode)->left == node) {
                        (*plastNode)->left = node->left;
                        delete node;
                        return;
                    }
                }
                // 兩個節點的情況
                Node *star = min(node->right);
                star->right = deleteMin(node->right);
                star->left = node->left;
            }
        }
    }
};

template <typename Key, typename Value>
std::ostream& operator<<(std::ostream &out, BinarySearchTree<Key, Value> &tree)
{
    tree.traverse(tree.root, out);
    return out;
}


#endif