public class Node{
public E e;
public Node left,right;
public Node(E e){
this.e = e;
right = null;
left = null;
}
}
- BST的API
- 需求
- 增:add
- 删:remove removeMax removeMin
- 改:
- 查:minimum maximum contains size isEmpty preOrder inOrder postOrder levelOrder
public class BST<E extends Comparable<E>>{
private Node root;
private int size;
public BST(){
root = null;
size = 0;
}
public void add(E e){
root = add(root,e);
}
private Node add(Node node, E e){
if(node == null){
size++;
return new Node(e);
}
if(e.compareTo(node.e)>0){
return add(node.right,e);
}else if(e.compareTo(node.e)<0){
return add(node.left,e);
}else{
return node;
}
}
public E removeMin(){
E ret = minimum();
removeMin(root);
return ret;
}
private Node removeMin(Node node){
if(node.left==null){
Node rightNode = node.right;
node.right = null;
size--;
return rightNode;
}
node.left = removeMin(node.left);
return node;
}
public E removeMax(){
E ret = maximum();
removeMax(root);
return ret;
}
private Node removeMax(Node node){
if(node.left==null){
Node leftNode = node.left;
node.left = null;
size--;
return leftNode;
}
node.right = removeMax(node.right);
return node;
}
public void remove(E e){
remove(root,e);
}
private Node remove(Node node,E e){
if(Node == null){
return null;
}
if(e.compareTo(node.e)<0){
node.left = remove(node.left,e);
return node;
}else if(e.compareTo(node.e) > 0){
node.right = remove(node.right,e);
return node;
}else{
if(node.left == null){
Node rightNode = node.right;
node.right = null;
size--;
return rightNode;
}
if(node.right == null){
Node leftNode = node.left;
node.left = null;
size--;
return leftNode;
}
Node successor = minimum(node.left);
successor.right = removeMin(node.right);
successor.left = node.left;
node.right = node.left = null;
return successor;
}
public int size(){
return size;
}
public boolean isEmpty(){
return size == 0;
}
public boolean contains(E e){
return contains(root,e);
}
private boolean contains(Node node,E e){
if(node == null){
return false;
}
if (e.compareTo(node.e) == 0) {
return true;
} else if (e.compareTo(node.e) < 0) {
return contains(node.left, e);
} else {
return contains(node.right, e);
}
}
public void preOrder(){
preOrder(root);
}
private void preOrder(Node node){
if(node == null){
return;
}
System.out.println(node.e);
preOrder(node.left);
preOrder(node.right);
}
public void inOrder(){
inOrder(root);
}
private void inOrder(Node node){
if(node == null){
return;
}
inOrder(node.left);
System.out.println(node.e);
inOrder(node.right);
}
public void postOrder(){
postOrder(root);
}
private void postOrder(Node node){
if(node == null){
return;
}
postOrder(node.left);
postOrder(node.right); System.out.println(node.e);
}
private void levelOrder(){
Queue<E> queue = new LinkedList<>();
queue.add(root);
while(!queue.isEmpty()){
Node cur = queue.remove();
if(cur.left!=null){
queue.add(cur.left);
}
if(cur.right!=null){
queue.add(cur.right);
}
}
}
public E minimum(){
if (size == 0) {
throw new IllegalArgumentException("BST is empty");
}
return minimum(root).e;
}
private Node minimum(Node node){
if (node.left == null) {
return node;
} else {
return minimum(node.left);
}
}
private Node miniNR(Node node){
while (node.left != null) {
node = node.left;
}
return node;
}
public E maximum(){
if (size == 0) {
throw new IllegalArgumentException("BST is empty");
}
return maximum(root).e;
}
private Node maximum(Node node){
if (node.right == null) {
return node;
} else {
return minimum(node.right);
}
}
private Node maxiNR(Node node){
while (node.right != null) {
node = node.right;
}
return node;
}
}