《数据结构：邓俊辉版》——二叉树的非递归先序遍历

1、构建二叉树的代码

这里为了方便，暂时没用T data。

template <typename T> class CTreeNode
{
public:
    CTreeNode();
    ~CTreeNode();

public:
    T data;
    int nData;
    CTreeNode* pLChild;
    CTreeNode* pRChild;

};

template <typename T>
CTreeNode<T>::~CTreeNode()
{

}

template <typename T>
CTreeNode<T>::CTreeNode() :
nData(0),
pLChild(NULL),
pRChild(NULL)
{

}

构建二叉树：

template <typename T> void BuildBinTree(int i, CTreeNode<T>** ppTreeNode)
{
    if (i < _countof(g_szArray))
    {
        *ppTreeNode = new(CTreeNode<T>);
        (*ppTreeNode)->nData = g_szArray[i];
        printf("%d ", g_szArray[i]);
    }
    else
    {
        return;
    }

    if (2 * i + 1 < _countof(g_szArray))
    {
        printf("l:");
        BuildBinTree(2 * i + 1, &(*ppTreeNode)->pLChild);
    }

    if (2 * i + 2 < _countof(g_szArray))
    {
        printf("r:");
        BuildBinTree(2 * i + 2, &(*ppTreeNode)->pRChild);
    }
}

2、构建一个简单的栈的代码：

template <typename T> class CStack
{
public:
    CStack();
    ~CStack();
    void Push(CTreeNode<T>*);
    CTreeNode<T>* Pop();
    BOOL IsEmpty();

private:
    CTreeNode<T>** m_szTreeNodeArray;
    int m_nSize;
    int m_nCapacity;
};

template <typename T>
BOOL CStack<T>::IsEmpty()
{
    return !m_nSize;
}

template <typename T>
CTreeNode<T>* CStack<T>::Pop()
{
    return m_szTreeNodeArray[--m_nSize];
}

template <typename T>
void CStack<T>::Push(CTreeNode<T>* pTreeNode)
{
    if (!pTreeNode)
    {
        return;
    }

    if (!m_szTreeNodeArray)
    {
        return;
    }

    if (m_nSize > m_nCapacity)
    {
        //realloc
    }

    m_szTreeNodeArray[m_nSize++] = pTreeNode;
}

template <typename T>
CStack<T>::CStack() :
m_nSize(0),
m_nCapacity(INIT_STACK_CAPACITY),
m_szTreeNodeArray(NULL)
{
    m_szTreeNodeArray = new CTreeNode<T>*[INIT_STACK_CAPACITY];
    if (!m_szTreeNodeArray)
    {
        return;
    }
}

template <typename T>
CStack<T>::~CStack()
{
    if (m_szTreeNodeArray)
    {
        free(m_szTreeNodeArray);
    }
}

3、非递归遍历的逻辑

CStack<int> g_stack;

template <typename T>
void NonRecursiveTraverse(CTreeNode<T>* pTreeNode)
{
    while (true)
    {
        while (pTreeNode)
        {
            printf("Visit Node:%d ", pTreeNode->nData);
            g_stack.Push(pTreeNode->pRChild);
            pTreeNode = pTreeNode->pLChild;
        }
        
        if (g_stack.IsEmpty())
        {
            break;
        }

        if (!g_stack.IsEmpty())
        {
            pTreeNode = g_stack.Pop();
        }
    }
}

4、main函数

#define INIT_STACK_CAPACITY 50

int g_szArray[] = { 1, 3, 2, 4, 7, 5, 6, 8 };


void main()
{
    CTreeNode<int>* pTreeNode = NULL;
    BuildBinTree<int>(0, &pTreeNode);

    printf("\nNon recurisive traverse:\n");
    NonRecursiveTraverse(pTreeNode);
    getchar();
}

5、运行结果