第五十八课 树形结构的层次遍历

通用树结构是一种容器，里面装有数据元素，我们有遍历元素的需求。

 非线性决定了树中的每个结点没有固定的编号方式。

将队列中队首的指针定义成遍历时的游标，根节点进入队列后，游标指向根节点。

队头元素弹出，队首的指针就指向了别的元素，这就相当于移动了游标。

添加遍历相关的程序：

#ifndef GTREE_H
#define GTREE_H

#include "Tree.h"
#include "GTreeNode.h"
#include "Exception.h"
#include "LinkQueue.h"

namespace DTLib
{

template < typename T >
class GTree : public Tree<T>
{
protected:
    LinkQueue<GTreeNode<T>*> m_queue;

    GTree(const GTree<T>&);
    GTree<T>& operator = (const GTree<T>&);

    GTreeNode<T>* find(GTreeNode<T>* node, const T& value) const
    {
        GTreeNode<T>* ret = NULL;

        if( node != NULL )
        {
            if( node->value == value )
            {
                return node;
            }
            else
            {
                for(node->child.move(0); !node->child.end() && (ret == NULL); node->child.next())
                {
                    ret = find(node->child.current(), value);
                }
            }
        }

        return ret;
    }

    GTreeNode<T>* find(GTreeNode<T>* node,  GTreeNode<T>* obj) const
    {
        GTreeNode<T>* ret = NULL;

        if( node == obj )
        {
            return node;
        }
        else
        {
            if( node != NULL )
            {
                for( node->child.move(0); !node->child.end() && (ret == NULL); node->child.next())
                {
                    ret = find(node->child.current(), obj);
                }
            }
        }

        return ret;
    }

    void free(GTreeNode<T>* node)
    {
        if( node != NULL )
        {
            for(node->child.move(0); !node->child.end(); node->child.next())
            {
                free(node->child.current());
            }

            if( node->flag() )
            {
                delete node;
            }
        }
    }

    void remove(GTreeNode<T>* node, GTree<T>*& ret)
    {
        ret = new GTree<T>();

        if( ret == NULL )
        {
            THROW_EXCEPTION(NoEnoughMemoryException, "No memory to create tree...");
        }
        else
        {
            if( root() == node )
            {
                this->m_root = NULL;
            }
            else
            {
                LinkList<GTreeNode<T>*>& child = dynamic_cast<GTreeNode<T>*>(node->parent)->child;

                child.remove(child.find(node));

                node->parent = NULL;
            }

            ret->m_root = node;
        }
    }

    int count(GTreeNode<T>* node) const
    {
        int ret = 0;

        if( node != NULL )
        {
            ret = 1;

            //node如果没有孩子，则for不执行
            for(node->child.move(0); !node->child.end(); node->child.next())
            {
                ret += count(node->child.current());
            }
        }

        return ret;
    }

    int height(GTreeNode<T>* node) const
    {
        int ret = 0;

        if( node != NULL )
        {
            for(node->child.move(0); !node->child.end(); node->child.next())
            {
                int h = height(node->child.current());

                if( ret < h )
                {
                    ret = h;
                }
            }

            ret = ret + 1;
        }

        return ret;
    }

    int degree(GTreeNode<T>* node) const
    {
        int ret = 0;

        if( node != NULL )
        {
            ret = node->child.length();  //根节点的度数

            for(node->child.move(0); !node->child.end(); node->child.next())
            {
                int d = degree(node->child.current());

                if( ret < d )
                {
                    ret = d;
                }
            }
        }

        return ret;
    }
public:
    GTree()
    {

    }
    bool insert(TreeNode<T>* node)
    {
        bool ret = true;

        if( node != NULL )
        {
            if( this->m_root == NULL ) //如果待插入节点的父节点为空，则这个节点将为根节点
            {
                node->parent = NULL;
                this->m_root = node;
            }
            else
            {
                GTreeNode<T>* np = find(node->parent);

                if( np != NULL )
                {
                    GTreeNode<T>* n = dynamic_cast<GTreeNode<T>*>(node);

                    if( np->child.find(n) < 0 )
                    {
                        np->child.insert(n);
                    }
                }
                else
                {
                    THROW_EXCEPTION(InvalidParameterException, "Invalid parent tree node...");
                }
            }
        }
        else
        {
            THROW_EXCEPTION(InvalidParameterException, "Parameter node cannot be NULL ...");
        }

        return ret;
    }

    bool insert(const T& value, TreeNode<T>* parent)
    {
        bool ret = true;

        GTreeNode<T>* node = GTreeNode<T>::NewNode();

        if( node != NULL )
        {
            node->value = value;
            node->parent = parent;

            insert(node);
        }
        else
        {
            THROW_EXCEPTION(NoEnoughMemoryException, "No memory to create node ...");
        }

        return ret;
    }

    //删除的节点的子节点我们还需要处理，因此要返回删除节点的指针，这样有机会对里面的元素做进一步操作
    SharedPointer< Tree<T> > remove(const T& value)
    {
        GTree<T>* ret = NULL;

        GTreeNode<T>* node = find(value);

        if( node == NULL )
        {
            THROW_EXCEPTION(InvalidParameterException, "can not find the node ...");
        }
        else
        {
            remove(node, ret);

            m_queue.clear();
        }

        return ret;
    }

    SharedPointer< Tree<T> > remove(TreeNode<T>* node)
    {
        GTree<T>* ret = NULL;

        node = find(node);

        if( node == NULL )
        {
            THROW_EXCEPTION(InvalidParameterException, "parameter node is invalid ...");
        }
        else
        {
            remove(dynamic_cast<GTreeNode<T>*>(node), ret);

            m_queue.clear();
        }

        return ret;
    }

    GTreeNode<T>* find(const T& value) const  // 返回GTreeNode，赋值兼容性
    {
        return find(root(), value);
    }

    GTreeNode<T>* find(TreeNode<T>* node) const
    {
        return find(root(), dynamic_cast<GTreeNode<T>*>(node));
    }

    GTreeNode<T>* root() const
    {
        return dynamic_cast<GTreeNode<T>*>(this->m_root);
    }

    int degree() const
    {
        return degree(root());
    }
    int count() const
    {
        return count(root());
    }

    int height() const
    {
        return height(root());
    }

    void clear()
    {
        free(root());

        this->m_root = NULL;

        m_queue.clear();
    }

    bool begin()
    {
        bool ret = ( root() != NULL );

        if( ret )
        {
            m_queue.clear();
            m_queue.add(root());
        }

        return ret;
    }

    bool end()
    {
        return (m_queue.length() == 0);
    }

    bool next()
    {
        bool ret = (m_queue.length() > 0);

        if( ret )
        {
            GTreeNode<T>* node = m_queue.front();

            m_queue.remove();  //将对头元素出队，相当于移动游标

            for(node->child.move(0); !node->child.end(); node->child.next())
            {
                m_queue.add(node->child.current());
            }
        }

        return ret;
    }

    T current()
    {
        if( !end() )  //遍历的过程当中调用current函数才有意义
        {
            return m_queue.front()->value;
        }
        else
        {
            THROW_EXCEPTION(InvalidOperationException, "No value at current position...");
        }
    }

    ~GTree()
    {
        clear();
    }
};

}

#endif // GTREE_H

测试程序如下：

#include <iostream>
#include "GTree.h"
#include "GTreeNode.h"


using namespace std;
using namespace DTLib;


int main()
{
    GTree<char> t;
    GTreeNode<char>* node = NULL;
    GTreeNode<char> root;

    root.value = 'A';
    root.parent = NULL;

    t.insert(&root);

    node = t.find('A');
    t.insert('B', node);
    t.insert('C', node);
    t.insert('D', node);

    node = t.find('B');
    t.insert('E', node);
    t.insert('F', node);

    node = t.find('E');
    t.insert('K', node);
    t.insert('L', node);

    node = t.find('C');
    t.insert('G', node);

    node = t.find('D');
    t.insert('H', node);
    t.insert('I', node);
    t.insert('J', node);

    node = t.find('H');
    t.insert('M', node);

    cout << t.degree() << endl;

    for(t.begin(); !t.end(); t.next())
    {
        cout << t.current() << endl;
    }

    return 0;
}

结果如下：

小结：