data-structures-and-algorithms/homework4/BiTree.h

#ifndef BITREE_H
#define BITREE_H

#include <iostream>
#include <sstream>
#include <string>
#include <unordered_map>

template <typename T>
class BiTree
{
public:
    T data;
    BiTree* left;
    BiTree* right;

    BiTree() : left(nullptr), right(nullptr)
    {
    }

    BiTree(char val): data(val), left(nullptr), right(nullptr)
    {
    }

    static bool is_empty(BiTree* bt)
    {
        if (bt == nullptr)
        {
            return true;
        }
        return false;
    }

    static bool is_leaf(BiTree* bt)
    {
        if (bt->left == nullptr && bt->right == nullptr)
        {
            return true;
        }
        return false;
    }

    static T sum_leaf(BiTree* bt)
    {
        if (is_empty(bt))
        {
            return 0;
        }
        if (is_leaf(bt))
        {
            return bt->data;
        }
        return sum_leaf(bt->left) + sum_leaf(bt->right);
    }

    static BiTree* createNode(const T& value)
    {
        BiTree* node = new BiTree();
        node->data = value;
        node->left = nullptr;
        node->right = nullptr;
        return node;
    }

    static void insertNode(BiTree*& bt, T value)
    {
        if (bt == nullptr)
        {
            bt = createNode(value);
        }
        else
        {
            if (value < bt->data)
            {
                insertNode(bt->left, value);
            }
            if (value > bt->data)
            {
                insertNode(bt->right, value);
            }
        }
    }

    static BiTree* buildFromPreorderString(const std::string& preorder, size_t& index)
    {
        if (index >= preorder.size() || preorder[index] == '#')
        {
            index++;
            return nullptr;
        }
        BiTree* node = createNode(preorder[index++]);
        node->left = buildFromPreorderString(preorder, index);
        node->right = buildFromPreorderString(preorder, index);
        return node;
    }

    void inorderTraversal(std::ostringstream& oss) const
    {
        if (left) left->inorderTraversal(oss);
        oss << data;
        if (right) right->inorderTraversal(oss);
    }

    static BiTree* buildFromPreorderInorderString(const std::string& preorder, const std::string& inorder, int preStart,
                                                  int preEnd,
                                                  int inStart, int inEnd, std::unordered_map<char, int>& inMap)
    {
        if (preStart > preEnd || inStart > inEnd)
        {
            return nullptr;
        }

        char rootVal = preorder[preStart];
        BiTree* root = new BiTree(rootVal);

        int inRoot = inMap[rootVal];
        int leftSubtreeSize = inRoot - inStart;

        root->left = buildFromPreorderInorderString(preorder, inorder, preStart + 1, preStart + leftSubtreeSize,
                                                    inStart, inRoot - 1, inMap);
        root->right = buildFromPreorderInorderString(preorder, inorder, preStart + leftSubtreeSize + 1, preEnd,
                                                     inRoot + 1, inEnd, inMap);


        return root;
    }

    static int getHeight(BiTree* root)
    {
        if (root == nullptr)
        {
            return 0;
        }
        int leftHeight = getHeight(root->left);
        int rightHeight = getHeight(root->right);
        return 1 + std::max(leftHeight, rightHeight);
    }

    void toStringHelper(std::ostringstream& oss, const std::string& prefix, bool isLeft, bool hasSibling) const
    {
        if (this != nullptr)
        {
            oss << prefix;
            oss << (isLeft ? (hasSibling ? "├─" : "└─") : (hasSibling ? "├─" : "└─")) << data << "\n";

            std::string newPrefix = prefix + (isLeft ? (hasSibling ? "│  " : "   ") : "   ");
            bool hasLeftSibling = (left != nullptr && right != nullptr);

            if (left) left->toStringHelper(oss, newPrefix, true, hasLeftSibling);
            if (right) right->toStringHelper(oss, newPrefix, false, false);
        }
    }

    std::string toString() const
    {
        std::ostringstream oss;
        this->toStringHelper(oss, "", false, false);
        return oss.str();
    }

    void destroy()
    {
        if (left)
        {
            left->destroy();
            delete left;
        }
        if (right)
        {
            right->destroy();
            delete right;
        }
    }
};

#endif // BITREE_H