C语言数据结构のBST树(写法一:非指针引用，非递归)

实现

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

#define true 1
#define false 0

typedef int elementType;

typedef struct bst
{
    elementType data;   // 数据域
    struct bst *left;   // 左指针
    struct bst *right;  // 右指针
}BST,*PBST;

PBST create_bst(int root_data);     // create include the root node tree
int insert_node(PBST bst,int data); // insert into bst
PBST create_node(PBST child,int data);
void print_inorder(PBST tree);

void main()
{
    int in;
    printf("请输入根节点的值");
    scanf("%d",&in);

    PBST bst = create_bst(in);
    insert_node(bst,2);
//    insert_node(bst,3);
    insert_node(bst,4);
    insert_node(bst,1);
//    insert_node(bst,6);
//    printf("\n%d",bst->right == NULL);
//    printf("\n%d",bst->left->data);
    print_inorder(bst);
}

PBST create_bst(int root_data)
{
    // 申请内存，并且返回地址
    PBST bst = (PBST)malloc(sizeof(PBST));
    if(bst == NULL)
    {
        printf("malloc apply fail");
        exit(-1);
    }

    bst->data = root_data; // 默认为0
    bst->left = NULL; // 防止出现野指针
    bst->right = NULL; // 防止出现野指针

    return bst;
}

PBST create_node(PBST child,int data)
{
    child = (PBST)malloc(sizeof(PBST));
    if(child==NULL)
    {
        printf("malloc apply fail - child");
        exit(-1);
    }
    child->data = data;
    child->left = child->right = NULL;

    return child;
}

// 中序排列（递增排列）
int insert_node(PBST bst,int data)
{
    PBST current_node = bst;
        if(current_node->data > data)
        {
            while(true){
                if(current_node->left !=NULL)
                {
                    current_node = current_node->left;
                }else
                {
                    PBST child = (PBST)malloc(sizeof(PBST));
                    child = create_node(child,data);

                    printf("\nchild data : %d \n",child->data);

                    current_node->left = child;

                   break;
                }
            }
        }else{
            while(true){
                if(current_node->right !=NULL)
                {
                    current_node = current_node->right;
                }else
                {
                    PBST child = (PBST)malloc(sizeof(PBST));
                    child = create_node(child,data);

                    printf("\nchild data : %d \n",child->data);

                    current_node->right = child;

                  break;
                }
           }
        }
}

void print_inorder(PBST tree) {
    if(tree) {
        print_inorder(tree->left);
        printf("%d\n",tree->data);
        print_inorder(tree->right);
    }
}