Question

i’m trying to implement some functions that allow me to add “Books” to a binary search tree for the “Student” class, but I’m getting a strange error:

msvcr100d.dll!strcmp(unsigned char * str1, unsigned char * str2) Line 83 Asm

The program is entirely in C/C++, so I’m not sure why its returning an assembly language error? My first thought is something is wrong with my use of strcmp, and the Call Stack shows Line 188 as the last executed statement (before the above error), which means I’m probably messing up my recursion somewhere. I am calling the insertBook() function of “Student”, so here is my “Student” class. Any help? Thanks.

class Student : public Personnel { //inherit from Personnel
public:
    Book *bookTree;

    Book* searchBookTree(Book *bookNode, char *title) {
        if ((strcmp(title, bookNode->title)) < 0) //***LINE 188
            return searchBookTree(bookNode->left, title); 

        else if ((strcmp(title, bookNode->title)) > 0)
            return searchBookTree(bookNode->right, title);

        else
            return bookNode;
    }

    void insertBook(Book *node) {
        Book *newBook, *parent;
        newBook = node;

        newBook->left = NULL;
        newBook->right = NULL;

        if (bookTree == NULL) { //if bookTree is empty
            bookTree = newBook; 
        }
        else {          
            parent = searchBookTree(bookTree, newBook->title);
            newBook->left = parent->left;
            newBook->right = parent->right;
        }   
    }

    void printBooks(Book *top) {
        Book *root = top;
        if (root != NULL) {
            printBooks(root->left);
            cout << "BOOK LIST" << endl;
            cout << "Title:\t\t" << root->title << endl;
            cout << "URL:\t\t" << root->url << endl;
            printBooks(root->right);
        }
    } 

    void display() {
            Personnel::display();
            cout << "STUDENT" << endl;  
            cout << "Level:\t\t" << getLevel() << endl;
            printBooks(bookTree); cout << endl;
    }

    Student(char *cName, char *cBirthday, char *cAddress, char *cPhone, char *cEmail, level gradeLevel) 
        : Personnel(cName, cBirthday, cAddress, cPhone, cEmail) 
    {
        bookTree = NULL;
        setLevel(gradeLevel);
    }

};

Answer 1

Book* searchBookTree(Book *bookNode, char *title) {
        if ((strcmp(title, bookNode->title)) < 0) //***LINE 188
            // What happens if bookNode->left == NULL ???
            return searchBookTree(bookNode->left, title); 

        else if ((strcmp(title, bookNode->title)) > 0)
            // What happens if bookNode->right== NULL ???
            return searchBookTree(bookNode->right, title);

        else
            return bookNode;
    }

you’ll need a termination point in your search function. At the top, I’d first check if bookNode == NULL.