Exer13_28_TreeNode_point.h

#ifndef EXER13_28_1_POINT_H
#define EXER13_28_1_POINT_H
#include <iostream>
#include <string>
#include <cstddef>
class TreeNode {
public:
    TreeNode() : count(0), left(nullptr), right(nullptr), use(new std::size_t(1)) {} // an empty node
    TreeNode(const std::string &s) : value(s), count(1), left(nullptr), right(nullptr), use(new std::size_t(1)) {}
    TreeNode(const TreeNode &tp):
        value(tp.value), count(tp.count), left(tp.left), right(tp.right), use(tp.use) { ++*use; }
    TreeNode& operator=(const TreeNode&);
    std::ostream& read(std::ostream& os) const { os << value << "\t" << count; return os; }
    void write(const std::string &str) { value = str; }
    ~TreeNode();
private:
    std::string value;
    int count;
    TreeNode *left;
    TreeNode *right;
    std::size_t *use;
};
TreeNode& TreeNode::operator=(const TreeNode& tp)
{
    ++*tp.use;
    if(--*use == 0)
    {
        if(left)
            delete left;
        if(right)
            delete right;
        delete use;
    }
    value = tp.value;
    count = tp.count;
    left = tp.left;
    right = tp.right;
    use = tp.use;
    return *this;
}
TreeNode::~TreeNode()
{
    if(--*use == 0)
    {
        if(left) {
            delete left;
            left = nullptr;
        }
        if(right) {
            delete right;
            right = nullptr;
        }
        delete use;
    }
}
#endif
// Note: one thing we have to watch out for is that left and child might hold
// null. This version is easier to handle than value-like version.