版权声明：欢迎转载并请注明出处，谢谢~~ https://blog.csdn.net/chimomo/article/details/85249234
package chimomo.learning.java.datastructure;
/**
* Implements an unbalanced binary search tree.
* Note that all "matching" is based on the compareTo method.
*
* @author Created by Chimomo
*/
public class BinarySearchTree<T extends Comparable<? super T>> {
/**
* The tree root.
*/
private BinaryNode<T> root;
/**
* Construct the tree.
*/
public BinarySearchTree() {
root = null;
}
// Test program
public static void main(String[] args) throws Exception {
// Create binary search tree.
BinarySearchTree<Integer> t = new BinarySearchTree<>();
final int NUMS = 4000;
final int GAP = 37;
// Insert.
for (int i = GAP; i != 0; i = (i + GAP) % NUMS) {
t.insert(i);
}
// Get height.
System.out.println("Height: " + t.height(t.root));
// Remove.
for (int i = 1; i < NUMS; i += 2) {
t.remove(i);
}
System.out.println("Checking... (no more output means success)");
// Print tree.
if (NUMS < 40) {
t.printTree();
}
// Find min and find max.
if (t.findMin() != 2 || t.findMax() != NUMS - 2) {
System.out.println("FindMin or FindMax error!");
}
// Contains.
for (int i = 2; i < NUMS; i += 2) {
if (!t.contains(i)) {
System.out.println("Find error1!");
}
}
for (int i = 1; i < NUMS; i += 2) {
if (t.contains(i)) {
System.out.println("Find error2!");
}
}
}
/**
* Insert into the tree; duplicates are ignored.
*
* @param x The item to insert.
*/
public void insert(T x) {
root = insert(x, root);
}
/**
* Remove from the tree. Nothing is done if x is not found.
*
* @param x The item to remove.
*/
public void remove(T x) {
root = remove(x, root);
}
/**
* Find the smallest item in the tree.
*
* @return The smallest item or null if empty.
*/
public T findMin() throws Exception {
if (isEmpty()) {
throw new Exception("Binary search tree is empty!");
}
return findMin(root).element;
}
/**
* Find the largest item in the tree.
*
* @return The largest item of null if empty.
*/
public T findMax() throws Exception {
if (isEmpty()) {
throw new Exception("Binary search tree is empty!");
}
return findMax(root).element;
}
/**
* Find an item in the tree.
*
* @param x The item to search for.
* @return True if found, false otherwise.
*/
public boolean contains(T x) {
return contains(x, root);
}
/**
* Make the tree logically empty.
*/
public void makeEmpty() {
root = null;
}
/**
* Test if the tree is logically empty.
*
* @return True if empty, false otherwise.
*/
public boolean isEmpty() {
return root == null;
}
/**
* Print the tree contents in sorted order.
*/
public void printTree() {
if (isEmpty()) {
System.out.println("Empty binary search tree");
} else {
printTree(root);
}
}
/**
* Internal method to insert into a subtree.
*
* @param x The item to insert.
* @param t The node that roots the subtree.
* @return The new root of the subtree.
*/
private BinaryNode<T> insert(T x, BinaryNode<T> t) {
if (t == null) {
return new BinaryNode<>(x, null, null);
}
int compareResult = x.compareTo(t.element);
if (compareResult < 0) {
t.left = insert(x, t.left);
} else if (compareResult > 0) {
t.right = insert(x, t.right);
} else {
// Duplicate; do nothing.
}
return t;
}
/**
* Internal method to remove from a subtree.
*
* @param x The item to remove.
* @param t The node that roots the subtree.
* @return The new root of the subtree.
*/
private BinaryNode<T> remove(T x, BinaryNode<T> t) {
// Item not found; do nothing.
if (t == null) {
return null;
}
int compareResult = x.compareTo(t.element);
if (compareResult < 0) {
t.left = remove(x, t.left);
} else if (compareResult > 0) {
t.right = remove(x, t.right);
} else if (t.left != null && t.right != null) { // Two children
t.element = findMin(t.right).element;
t.right = remove(t.element, t.right);
} else {
t = (t.left != null) ? t.left : t.right;
}
return t;
}
/**
* Internal method to find the smallest item in a subtree.
*
* @param t The node that roots the subtree.
* @return The node containing the smallest item.
*/
private BinaryNode<T> findMin(BinaryNode<T> t) {
if (t == null) {
return null;
} else if (t.left == null) {
return t;
}
return findMin(t.left);
}
/**
* Internal method to find the largest item in a subtree.
*
* @param t The node that roots the subtree.
* @return The node containing the largest item.
*/
private BinaryNode<T> findMax(BinaryNode<T> t) {
if (t != null) {
while (t.right != null) {
t = t.right;
}
}
return t;
}
/**
* Internal method to find an item in a subtree.
*
* @param x The item to search for.
* @param t The node that roots the subtree.
* @return True if contains, false otherwise.
*/
private boolean contains(T x, BinaryNode<T> t) {
if (t == null) {
return false;
}
int compareResult = x.compareTo(t.element);
if (compareResult < 0) {
return contains(x, t.left);
} else if (compareResult > 0) {
return contains(x, t.right);
} else {
return true; // Match
}
}
/**
* Internal method to print a subtree in sorted order.
*
* @param t The node that roots the subtree.
*/
private void printTree(BinaryNode<T> t) {
if (t != null) {
printTree(t.left);
System.out.println(t.element);
printTree(t.right);
}
}
/**
* Internal method to compute height of a subtree.
*
* @param t The node that roots the subtree.
*/
private int height(BinaryNode<T> t) {
if (t == null) {
return -1;
} else {
return 1 + Math.max(height(t.left), height(t.right));
}
}
/**
* Basic node stored in unbalanced binary search trees.
*
* @param <AnyType> Any type
*/
private static class BinaryNode<AnyType> {
AnyType element; // The data in the node
BinaryNode<AnyType> left; // Left child
BinaryNode<AnyType> right; // Right child
// Constructors
BinaryNode(AnyType theElement) {
this(theElement, null, null);
}
BinaryNode(AnyType theElement, BinaryNode<AnyType> left, BinaryNode<AnyType> right) {
element = theElement;
this.left = left;
this.right = right;
}
}
}
/*
Output:
Height: 119
Checking... (no more output means success)
*/