Inserting into a binary search tree

Question

I wrote a function to insert nodes into a binary search tree. However, when trying to build a solution in Visual Studio 2013, I receive this: "Unhandled exception at 0x00FD4CD0 in BST.exe: 0xC0000005: Access violation reading location 0xCCCCCCCC." The following is my code.

void BST::insert(int value) {
    Node* temp = new Node();
    temp->data = value;
    if(root == NULL) {
        root = temp;
        return;
    }
    Node* current;
    current = root;
    Node* parent;
    parent = root;
    current = (temp->data < current->data) ? (current->leftChild) : (current->rightChild);
    while(current != NULL) {
        parent = current;
        current = (temp->data < current->data) ? (current->leftChild) : (current->rightChild);
    }
    if(temp->data < parent->data) {
        parent->leftChild = temp;
    }
    if(temp->data > parent->data) {
        parent->rightChild = temp;
    }
}

Then in my main function I have:

int main() {
    BST bst;
    bst.insert(10);
    system("pause");
}

When I remove bst.insert(10); in my main function, I no longer receive the unhandled exception.

The following is the initialization of my struct

struct Node {
    int data;
    Node* leftChild;
    Node* rightChild;
    Node() : leftChild(NULL), rightChild(NULL) {} 
};
struct BST {
    Node* root;
    void insert(int value);
    BST() : root(NULL) {}
};

Answer 1

In your insertion function you are not setting leftChild and rightChild to NULL.

void BST::insert(int value) {
    Node* temp = new Node();
    temp->data = value;
    temp->leftChild = NULL;
    temp->rightChild = NULL;
    if(root == NULL) {
        root = temp;
        return;
    }

Also, I cannot be sure (as you have not posted the constructor for BST ) but you may not have set root to NULL in the BST constructor. Try with these modifications.

Seems like you do not have a constructor in BST from what you have posted:

struct BST {
    Node* root;
    void insert(int value);
    BST(): root(NULL) { } // add a constructor to initialize root to NULL
};