二叉树的创建、打印、删除等函数（c）

我认为要看懂下面的代码，对于递归的运行，要很了解才是！

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#include <stdio.h>
#include <stdlib.h>

struct TreeNode;
typedef struct TreeNode *Position;
typedef struct TreeNode *SearchTree;

/* Placein the implement file */
struct TreeNode
{
    int Element;
    SearchTree Left;
    SearchTree Right;
};

/* clean up tree */
SearchTree MakeEmpty(SearchTree T)
{
    if (T != NULL)
    {
        MakeEmpty(T->Left);
        MakeEmpty(T->Right);
        free(T);
        T = NULL;
    }

    return NULL;
}

/* find x in the tree */
Position Find(int X, SearchTree T)
{
    if (T != NULL)
    {
        if (T->Element == X)
        {
            return T;
        }
        else if(T->Element < X)
        {
             return Find(X, T->Right);
        }
        else if (T->Element > X)
        {
            return Find(X, T->Left);
        }
    }
    else
    {
        return NULL;
    }
}

/* find min */
Position FindMin(SearchTree T)
{
    if (T == NULL)
    {
        return NULL;
    }
    else
    {
        if (T->Left != NULL)
        {
            FindMin(T->Left);
        }
        else
        {
            printf("MIN = %d\n", T->Element);
            return T;
        }
    }

}
/* find max */
Position FindMax(SearchTree T)
{
    if (T == NULL)
    {
        return NULL;
    }
    else
    {
        if (T->Right!= NULL)
        {
            FindMax(T->Right);
        }
        else
        {
            printf("MAX = %d\n", T->Element);
            return T;
        }
    }

}

/* insert x */
SearchTree Insert(int X, SearchTree T)
{
    if (T == NULL)
    {
        T = (SearchTree)malloc(sizeof(struct TreeNode));
        if (T == NULL)
        {
            printf("out of space!!!\n");
        }
        else
        {
            T->Element = X;
            T->Left = NULL;
            T->Right = NULL;
        }
    }
    else if (X < T->Element)
    {
        T->Left = Insert(X, T->Left);   //-----------------
    }
    else if (X > T->Element)
    {
        T->Right = Insert(X, T->Right); //----------------
    }

    return T;
}

/* delete x */
SearchTree DeleteTree(int X, SearchTree T)
{
    Position TmpCell;

    if (T == NULL)
    {
        printf("X not found.\n");
    }
    else
    {
        if (X < T->Element) /* go to left */
        {
            T->Left = DeleteTree(X, T->Left);
        }
        else if (X > T->Element)
        {
            T->Right = DeleteTree(X, T->Right);
        }
        else
        {
            if (T->Left && T->Right)   /* Two children */
    {
                /* replace with smallest in right subtree */

补充：软件开发 , C语言 ,