C++ //练习 13.28 给定下面的类，为其实现一个默认构造函数和必要的拷贝控制成员。

C++ Primer（第5版） 练习 13.28

练习 13.28 给定下面的类，为其实现一个默认构造函数和必要的拷贝控制成员。

( a )
class TreeNode{
	private:
	string value;
	int count;
	TreeNode *left;
	TreeNode *right;
};
( b )
class BinStrTree{
	private:
	TreeNode *root;
};

环境：Linux Ubuntu（云服务器）

工具：vim

代码块

( a )
class TreeNode {
private:
    std::string value;
    int count;
    TreeNode *left;
    TreeNode *right;

public:
    TreeNode(const std::string& val = std::string(), int cnt = 0): value(val), count(cnt), left(nullptr), right(nullptr) {}
    
    TreeNode(const TreeNode& other): value(other.value), count(other.count) {
        left = other.left ? new TreeNode(*other.left) : nullptr;
        right = other.right ? new TreeNode(*other.right) : nullptr;
    }
    
    ~TreeNode() {
        delete left;
        delete right;
    }
    
    TreeNode& operator=(const TreeNode& other) {
        if (this != &other) {
            TreeNode tmp(other);
            std::swap(value, tmp.value);
            std::swap(count, tmp.count);
            std::swap(left, tmp.left);
            std::swap(right, tmp.right);
        }
        return *this;
    }
};

( b )
class BinStrTree {
private:
    TreeNode *root;

public:
    BinStrTree() : root(nullptr) {}
    
    BinStrTree(const BinStrTree& other) {
        root = other.root ? new TreeNode(*other.root) : nullptr;
    }
    
    ~BinStrTree() {
        delete root;
    }
    
    BinStrTree& operator=(const BinStrTree& other) {
        if (this != &other) {
            BinStrTree tmp(other); // Copy-constructor
            std::swap(root, tmp.root);
        }
        return *this;
    }
};