搜索错误时收到搜索二叉树

Question

我真的无法应付的家伙。我该怎么解决这个问题。我不断收到我的 root 错误，它总是提到 root 是 nullptr。然后，突然间，我所有的书籍记录都消失了/删除。我不知道如何解决这个问题，我一直在使用 strcmp 进行更改，但没有它，但仍然如此。如果我找到搜索过的内容也是如此，它会删除我所有的书籍记录。也许你们可以为我提供一些需要修复的错误语法，并通过编码解释我的错误。 This is the snapshot of the error

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
struct node{
    char title[50], author[50], ISBN[50], pubDate[20], searchAuthor[50];
    struct node* left, * right;
};
struct node* delete_node(struct node* root, char deleteAuthor[]);
struct node* insert_node(struct node* root, char author[], char title[], char ISBN[], char pubDate[]);
struct node* FindMin(struct node*);
//struct node* search(struct node* root, char deleteAuthor[]);

void in_display(struct node* root);
void search(struct node* root, char searchAuthor[]);


void main()
{
    struct node* root = NULL;
    int ch, loop;
    char title[50], author[50], ISBN[50], pubDate[20], searchAuthor[50], deleteAuthor[50];
    printf("\n\n\t\t\tBinary Search Tree");
    printf("\n\t\t-- To stores a library of book records");
    printf("\n\t\t-- To search a library of book records");
    printf("\n\t\t-- To delete a library of book records");
    printf("\n\t\t-- To display a library of book records");
    printf("\n\t=========================================================\n");

    printf("\n\tState the number of book you need to input: ");
    scanf("%d", &loop);
    for (int c = 0; c < loop; c++) {
        printf("\n\n\t\t\t--------Insert New Book--------");
        printf("\n\tEnter the author of the book: \t\t\t");
        scanf("\n%[^\n]%*c", author);
        printf("\tEnter the title of the book: \t\t\t");
        scanf("\n%[^\n]%*c", title);
        printf("\tKey in the ISBN code: \t\t\t\t");
        scanf("\n%[^\n]%*c", ISBN);
        printf("\tEnter the Publication Date of the book: \t");
        scanf("\n%[^\n]%*c", pubDate);
        root = insert_node(root, author, title, ISBN, pubDate);
    }
    printf("\t\t\t--------Insert New Book End--------\n\n");
    printf("\n\tPlease enter choice (1/2/3/4/5) based on the ....");
    do
    {
        //printf("\n\t1.\tInsert a new Boook Record");
        printf("\n\t1.\tDisplay all the Books record");
        printf("\n\t2.\tDelete a Book Record");
        printf("\n\t3.\tSearch a abook Record ");
        printf("\n\t4.\tExit");
        printf("\n\n\tEnter your choice: ");
        scanf("%d", &ch);
        switch (ch){
        case 1:
            printf("\n\t\t-----------------Library of Book Records-----------------\n");
            in_display(root);
            break;
        case 2:
            printf("\nEnter the author of the book to be deleted: \t");
            scanf("\n%[^\n]%*c", deleteAuthor);
            root = delete_node(root, deleteAuthor);
            break;
        case 3:
            printf("\nEnter the author of the book to be searched: \t");
            scanf("\n%[^\n]%*c", searchAuthor);
            search(root, searchAuthor);
            break;
        case 4:
            exit(0);
            break;
        default: printf("\n\tWrong Option\n");
        }
    } while (1);
}
struct node* insert_node(struct node* root, char author[], char title[], char ISBN[], char pubDate[])
{
    if (root == NULL)
    {
        struct node* temp = (struct node*)malloc(sizeof(struct node));
        strcpy(temp->author, author);
        strcpy(temp->title, title);
        strcpy(temp->ISBN, ISBN);
        strcpy(temp->pubDate, pubDate);
        temp->left = NULL;
        temp->right = NULL;
        return temp;
    }
    if (strcmp(author, root->author)<=0)
    {
        root->left = insert_node(root->left, author, title, ISBN, pubDate);
    }
    else
    {
        root->right = insert_node(root->right, author, title, ISBN, pubDate);
    }
    return root;
}
void in_display(struct node* root) {
    
    if (root == NULL) {
        return;
    }
    in_display(root->left);
    printf("\n\tAuthor Name \t\t- %s", root->author);
    printf("\n\tBook Title \t\t- %s", root->title);
    printf("\n\tISBN \t\t\t- %s", root->ISBN);
    printf("\n\tPublication Date \t- %s\n", root->pubDate);
    in_display(root->right);
}
struct node* delete_node(struct node* root, char deleteAuthor[]) {
    if (root == NULL) {
        return root;
    }
    else if (strcmp(deleteAuthor, root->author) < 0) {
        root->left = delete_node(root->left, deleteAuthor);
        printf("\nBook Record Not Found\n");
    }
    else if (strcmp(deleteAuthor, root->author) > 0) {
        root->right = delete_node(root->right, deleteAuthor);
        printf("\nBook Record Not Found\n");
    }
    else {
        if (root->left == NULL && root->right == NULL) {
            free(root);
            root = NULL;
            printf("\nBook Record Successfully Deleted\n");
        }
        else if (root->left == NULL) {
            struct node* temp = root;
            root = root->right;
            free(temp);
            temp = NULL;
            printf("\nBook Record Successfully Deleted\n");
        }
        else if (root->right == NULL) {
            struct node* temp = root;
            root = root->left;
            free(temp);
            temp = NULL;
            printf("\nBook Record Successfully Deleted\n");
        }
        else {
            struct node* temp = root;
            root->left = FindMin(root);
            root->left->right = root->right;
            root = root->left;
            strcpy(temp->author, root->author);
            strcpy(temp->title, root->title);
            strcpy(temp->ISBN, root->ISBN);
            strcpy(temp->pubDate, root->pubDate);
            free(temp);
            temp = NULL;
            printf("\nBook Record Successfully Deleted\n");
        }
        return root;
    }
    return root;
}

struct node* FindMin(struct node* root) {
    while (root->left != NULL) {
        root = root->left;
    }
    return root;
}
void search(struct node* root, char searchAuthor[]){
    if (root->author < searchAuthor) {
        return search(root->right, searchAuthor);
    }
    else if (root->author > searchAuthor) {
        return search(root->left, searchAuthor);
    }
    else {
        printf("\n\t\t\t--------Searched Book Found--------\n");
        printf("\n\t\t\tAuthor Name \t\t- %s", root->author);
        printf("\n\t\t\tBook Title \t\t- %s", root->title);
        printf("\n\t\t\tISBN \t\t\t- %s", root->ISBN);
        printf("\n\t\t\tPublication Date \t- %s\n", root->pubDate);
        //return root;
    }
}

Answer 1

您的代码有很多需要改进的地方，但我只关注search 函数：

• 它应该处理root 是NULL 的情况。如果不这样做，当root 为NULL 时，您最终将访问root->left 或root-right，这会产生异常。

• 字符数组不会像现在这样比较。您的代码当前正在比较指针值。请改用strcmp。

• 当函数类型为void 时使用return 是矛盾的。我建议将函数的返回类型更改为struct * node，并让函数返回找到的节点（如果有），否则返回NULL。

所以：

struct node * search(struct node* root, char searchAuthor[]){
    if (root == NULL) {
        printf("\n Book not found");
        return NULL;
    }
    int diff = strcmp(root->author, searchAuthor);
    if (diff < 0) {
        return search(root->right, searchAuthor);
    }
    else if (diff > 0) {
        return search(root->left, searchAuthor);
    }
    else {
        printf("\n\t\t\t--------Searched Book Found--------\n");
        printf("\n\t\t\tAuthor Name \t\t- %s", root->author);
        printf("\n\t\t\tBook Title \t\t- %s", root->title);
        printf("\n\t\t\tISBN \t\t\t- %s", root->ISBN);
        printf("\n\t\t\tPublication Date \t- %s\n", root->pubDate);
        return root;
    }
}

对此函数的最后评论：最好从该函数（和其他函数）中删除所有打印，并且只在主代码中进行打印。这使您的函数独立于 I/O 事务，这是一件好事。