programming-examples/java/Data_Structures/BinarySearchTree.java

public class BinarySearchTree {

	Node root;

	static class Node {
		int key;
		int value;
		Node l;
		Node r;
		Node p;

		public Node(int key, int value, Node p) {
			this.key = key;
			this.value = value;
			this.p = p;
		}
	}

	Node search(Node t, int key) {
		if (t == null || t.key == key)
			return t;
		if (key < t.key)
			return search(t.l, key);
		else
			return search(t.r, key);
	}

	public Node search(int key) {
		return search(root, key);
	}

	Node insert(Node t, Node p, int key, int value) {
		if (t == null) {
			t = new Node(key, value, p);
		} else {
			if (key < t.key)
				t.l = insert(t.l, t, key, value);
			else
				t.r = insert(t.r, t, key, value);
		}
		return t;
	}

	public void insert(int key, int value) {
		root = insert(root, null, key, value);
	}

	void replace(Node a, Node b) {
		if (a.p == null)
			root = b;
		else if (a == a.p.l)
			a.p.l = b;
		else
			a.p.r = b;
		if (b != null)
			b.p = a.p;
	}

	void remove(Node t, int key) {
		if (t == null)
			return;
		if (key < t.key)
			remove(t.l, key);
		else if (key > t.key)
			remove(t.r, key);
		else if (t.l != null && t.r != null) {
			Node m = t.r;
			while (m.l != null)
				m = m.l;
			t.key = m.key;
			t.value = m.value;
			replace(m, m.r);
		} else if (t.l != null) {
			replace(t, t.l);
		} else if (t.r != null) {
			replace(t, t.r);
		} else {
			replace(t, null);
		}
	}

	public void remove(int key) {
		remove(root, key);
	}

	void print(Node t) {
		if (t != null) {
			print(t.l);
			System.out.print(t.key + ":" + t.value + " ");
			print(t.r);
		}
	}

	public void print() {
		print(root);
		System.out.println();
	}

	// Usage example
	public static void main(String[] args) {
		BinarySearchTree tree = new BinarySearchTree();
		tree.insert(3, 1);
		tree.insert(2, 2);
		tree.insert(4, 5);
		tree.print();

		tree.remove(2);
		tree.remove(3);
		tree.print();
		tree.remove(4);
	}
}