/// <summary>
/// Move node position after deleting
/// </summary>
/// <param name="parent"></param>
/// <param name="target"></param>
/// <param name="replace"></param>
private void UpdateMovieNode(MovieNode parent, MovieNode target, MovieNode replace)
{
if (parent.left == target)
{
parent.left = replace;
}
else
{
parent.right = replace;
}
}
/// <summary>
/// Add new movie to the tree
/// </summary>
/// <param name="movie">Movie object</param>
/// <returns>True if movie is added, False if movie already exists in the collection</returns>
public bool Add(Movie movie)
{
if (root == null)
{
root = new MovieNode(movie);
count++;
return(true);
}
MovieNode pin = root;
while (true)
{
// the title comes before the compared title
if (movie.CompareTo(pin.movie) < 0)
{
if (pin.left == null)
{
pin.left = new MovieNode(movie);
count++;
return(true);
}
pin = pin.left;
// the title comes after the compared title
}
else if (pin.movie.CompareTo(movie) < 0)
{
if (pin.right == null)
{
pin.right = new MovieNode(movie);
count++;
return(true);
}
pin = pin.right;
// the title is same as the compared title (pin.movie.CompareTo(movie) == 0)
// the movie should not be added to the tree
}
else
{
return(false);
}
}
}
/// <summary>
/// Get Movie object of title
/// </summary>
/// <param name="title">Movie title</param>
/// <returns>Movie object</returns>
public Movie GetMovie(string title)
{
MovieNode pin = root;
while (pin != null)
{
// found a movie
if (CompareMovie(pin.movie.title, title) == 0)
{
return(pin.movie);
// the movie should be on the left side of current pin
}
else if (CompareMovie(title, pin.movie.title) < 0)
{
pin = pin.left;
// the movie should be on the right side of current pin
}
else if (CompareMovie(pin.movie.title, title) < 0)
{
pin = pin.right;
}
}
return(null);
}
/// <summary>
/// Remove movie objct of title from tree
/// </summary>
/// <param name="title">Movie title that is to be deleted</param>
public void Remove(string title)
{
MovieNode parent = null;
MovieNode pin = root;
while (pin != null)
{
// found a target movie
if (CompareMovie(pin.movie.title, title) == 0)
{
// no children
if (pin.left == null && pin.right == null)
{
// current pin is root, so just empty the tree
if (pin == root)
{
root = null;
}
else
{
// pin to be null, parent's left or right to be null
UpdateMovieNode(parent, pin, null);
}
// has a child on the left hand side of current node (pin)
}
else if (pin.left != null && pin.right == null)
{
if (pin == root)
{
// root will be the node of the left hand side of current root
root = root.left;
}
else
{
// move pin's left to pin's position
UpdateMovieNode(parent, pin, pin.left);
}
// has a child on the right hand side of current node (pin)
}
else if (pin.left == null & pin.right != null)
{
if (pin == root)
{
root = root.right;
}
else
{
// move pin's right to pin's position
UpdateMovieNode(parent, pin, pin.right);
}
// has children on both side of current node (pin)
}
else
{
MovieNode scopeParent = pin;
MovieNode scopePin = pin.left;
// find right-most node in left subtree
while (scopePin.right != null)
{
scopeParent = scopePin;
scopePin = scopePin.right;
}
// no right subtree in pin's left subtree
// shift node up
if (scopeParent == pin)
{
pin.movie = scopePin.movie;
pin.left = scopePin.left;
// let scope parent to take over scope pin's left
// scope pin move to pin's (to be deleted) poistion
}
else
{
scopeParent.right = scopePin.left;
pin.movie = scopePin.movie;
}
}
count--;
return;
// title is on the left side of the pin
}
else if (CompareMovie(title, pin.movie.title) < 0)
{
parent = pin;
pin = pin.left;
// title is on the right side of the pin
}
else if (CompareMovie(pin.movie.title, title) < 0)
{
parent = pin;
pin = pin.right;
}
}
}
