程序代码：

typedef char Elemtype;

typedef struct BiTreeNode
{
    struct BiTreeNode *lChild;
    struct BiTreeNode *rChild;
    Elemtype           eData;
}T_BiTreeNode;

typedef struct DouLkBiTree
{
    T_BiTreeNode *ptRoot;    //    根结点
    int           iNum;
}T_DouBiTree;