c - C中二叉树遍历没有输出

Question

我是一名菜鸟程序员，我有一个项目需要使用二叉树。我所要做的就是插入一个节点，删除一个节点并添加树遍历的两种方法。问题是我无法让我的代码工作。我决定添加一些辅助函数，例如 check_element 和 create_NewNode 来帮助我更轻松地实现。运行后我的控制台上没有输出，或者它只是用运行时错误来问候我。我有一个头文件，IO.c 文件来存储我的函数和 main.c. 来测试头文件实现的函数。

Here is IO.c , used to store the functions.



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

    struct node{
        int data;
        struct node *left;
        struct node *right;

    };

    struct node *root;


    /*-----------------------------------------------------------------------------------------*/

        //function to determine if an element is already in the tree
    void check_element( struct node *node, int value)
    {
        while( node != NULL ){
            //checking if the value is here
            if( value == node->data ){
                printf("The element %d already exists in the tree!",value);
                exit(0);
            //if the value is smaller, go left
            }else if( value < node->data ){
                check_element( node->left, value );
            //else go right
            }else if( value > node->data ){
                check_element( node->right, value );
            //else the element was not found and we can add it to th tree
            }else{
                printf("Adding the element %d to the tree.",value);
                exit(0);
            }

        }//end while

    }//end check_element



    /*-----------------------------------------------------------------------------------------*/


        //helper function to crate a new node and set left and right pointers to NULL
    struct node *create_NewNode(  int value )
    {
        struct node *ptr;
        struct node *temp = (struct node*)malloc(sizeof(struct node));
        ptr = (struct node*)malloc(sizeof(struct node));

        if( ptr == NULL){
            printf("Memory allocation error!");
            exit(-1);
        }

        //assigning the data to the newly created node
        temp->data = value;

        //setting left and right pointers to NULL
        temp->left = NULL;
        temp->right = NULL;

        return temp;
    }


    /*-----------------------------------------------------------------------------------------*/


        //function to add a new value to the tree;
    struct node *insert_value( struct node *node, int new_value )
    {

        //checking if the element already exists to the tree
        check_element( node, new_value );

        //checking if the tree is empty
        if( node == NULL ){
            node = create_NewNode( new_value );
        //if the value is smaller, we add it to the left
        }else if( new_value < node->data ){
            insert_value( node->left, new_value );
        //else we add it to the right
        }else{
             insert_value( node->right, new_value );
        }

        return node;

    }


    /*-----------------------------------------------------------------------------------------*/


    void printPostorder( struct node *node )
    {
         if (node == NULL){
                printf("The tree is empty!");
                exit(0);
         }else{
                //first go left
                printPostorder( node->left );

                //then go right
                printPostorder( node->right );

                //finally, print the node value
                printf("%d", node->data);

         }
    }


    /*-----------------------------------------------------------------------------------------*/


    void inorder_traversal( struct node *node )
    {
       if( node == NULL) {
            printf("The tree is empty!");
            exit(0);
       }else{
            //first go left
            inorder_traversal( node->left );

            //print the node value
            printf("%d ",node->data);

            //then go right
            inorder_traversal( node->right );

       }
    }


    /*-----------------------------------------------------------------------------------------*/




This is the header file, called Library.h



 //prototype for NewNode
struct node *create_NewNode( int value );
    //prototype for insert_value
struct node *insert_value( struct node *node, int new_value );
    //prototype for printPostordre
void printPostorder( struct node* node);
    //prototype for printInorder
void inorder_traversal( struct node *node );
    //prototype for check_element
void check_element( struct node *node, int value);



And, finally, the main.c: `enter code here:



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

    int main()
    {
        // TEST CODE

        struct node *root;
        root = NULL;

        insert_value(root, 1);
        insert_value(root, 2);
        insert_value(root, 3);


         printPostorder( root );
        inorder_traversal( root );







        return 0;
    }


PS: I did my best to write this code, but, as I said, I am a rookie and I'm pretty bad at coding.I'd also like to appologize for any grammar mistakes, i am not an englishman.

Answer 1

可能还有更多错误，但我阅读了create_node()，并希望就此提出建议:

struct node *create_NewNode(  int value )
{
    struct node *ptr;
    struct node *temp = malloc(sizeof(struct node));
    ptr = malloc(sizeof(struct node));

    if( ptr == NULL){
        printf("Memory allocation error!");
        exit(-1);
    }

    //assigning the data to the newly created node
    temp->data = value;

    //setting left and right pointers to NULL
    temp->left = NULL;
    temp->right = NULL;

    return temp;
}

此处您要创建两个节点，而您打算只创建一个。您将 temp 视为新的，而您忘记了 ptr。您不需要创建另一个节点!

您需要的是树的指针，以便您在该树上添加新构造的节点(因此您可以将另一个参数传递给该函数，即树的指针)。

顺便说一句，我删除了 malloc 的转换，如 Do I cast the result of malloc? 中所述

---

我建议尝试根据我的建议修复您的代码。但是，我会将您链接到 treemanagement.c ，即 c一棵树的代码，完整的注释，这是我了解这种数据结构的方式，以后可能会派上用场!