Deletion in binary search tree

Question

So when I delete in binary search tree, do I need to have like 7 different cases i.e.

1. Left Leaf;
2. Right Leaf;
3. Left child with only left child.

Answer 1

You can keep it a lot simpler than that, and simply restrict yourself to three cases when deleting a node from a BST (binary search tree) :

1. a node without children (a leaf) : just remove it - nothing special needs to be done
2. a node with one child : remove it, and move the child in its place
3. a node with two children : swap it with either its in-order predecessor or successor, and then remove it

The wiki page contains an example of how this could look in code.

Or as a very basic example in C :

if (current->left==NULL && current->right==NULL) {
    /* leaf node */
    bst_replace(current, NULL);
}
else if (current->left==NULL || current->right==NULL) {
    /* node with one child */
    bst_replace(current, ((current->left) ? current->left : current->right));
}
else {
    /* node with two children */
    Node* successor = bst_next(current);
    current->data = successor->data;
    bst_replace(successor, successor->right);
}