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400 lines (358 loc) · 9.94 KB
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package code_08_trie;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
/**
* Created by 18351 on 2018/12/17.
*/
public class BST<E extends Comparable<E>> {
private Node root;
private int size;
public BST(){
root=null;
size=0;
}
public int size(){
return size;
}
public boolean isEmpty(){
return size==0;
}
private class Node{
public E e;
public Node left,right;
public Node(E e){
this.e=e;
this.left=null;
this.right=null;
}
}
/* //向BST中添加新元素e
public void add(E e){
if(root==null){
root=new Node(e);
size++;
return;
}else{
add(root,e);
}
}
//向以node为根节点的BST树种插入元素e
private void add(Node node,E e){
if(e.equals(node.e)){
//插入元素与根节点相等，直接返回
return;
}else if(e.compareTo(node.e)<0 && node.left==null){
node.left=new Node(e);
size++;
return;
}else if(e.compareTo(node.e)>0 && node.right==null){
node.right=new Node(e);
size++;
return;
}
if(e.compareTo(node.e)<0){
add(node.left,e);
}else{ //e.compareTo(node.e)>0
add(node.right,e);
}
}*/
//向BST中添加新元素e
public void add(E e){
root=add(root,e);
}
//向以node为根节点的BST树种插入元素e
//返回插入新元素后该BST的根
private Node add(Node node,E e){
if(node==null){
size++;
return new Node(e);
}
//注意：对于e.equals(node.e)不做处理
if(e.compareTo(node.e)<0){
node.left=add(node.left,e);
}else if(e.compareTo(node.e)>0){
node.right=add(node.right,e);
}
return node;
}
//查看BST中是否包含元素e
public boolean contains(E e){
return contains(root,e);
}
//查看以node为根节点的BST中是否包含元素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);
}
}
//BST的前序遍历
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);
}
//BST的前序遍历（非递归方式）
public void preOrderNR(){
preOrderNR(root);
}
private void preOrderNR(Node node){
if(node==null){
return;
}
Stack<StackNode> stack=new Stack<>();
stack.push(new StackNode(Command.GO,node));
while(!stack.isEmpty()){
StackNode stackNode=stack.pop();
Node n=stackNode.node;
Command command=stackNode.command;
if(command== Command.COUT){
System.out.println(stackNode.node.e);
}else{
if(n.right!=null){
stack.push(new StackNode(Command.GO,n.right));
}
if(n.left!=null){
stack.push(new StackNode(Command.GO,n.left));
}
stack.push(new StackNode(Command.COUT,n));
}
}
}
//BST的中序遍历
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);
}
//BST的中序遍历（非递归方式）
public void inOrderNR(){
inOrderNR(root);
}
private void inOrderNR(Node node){
if(node==null){
return;
}
Stack<StackNode> stack=new Stack<>();
stack.push(new StackNode(Command.GO,node));
while(!stack.isEmpty()){
StackNode stackNode=stack.pop();
Node n=stackNode.node;
Command command=stackNode.command;
if(command== Command.COUT){
System.out.println(stackNode.node.e);
}else{
if(n.right!=null){
stack.push(new StackNode(Command.GO,n.right));
}
stack.push(new StackNode(Command.COUT,n));
if(n.left!=null){
stack.push(new StackNode(Command.GO,n.left));
}
}
}
}
//BST的后序遍历
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);
}
//BST的后序遍历（非递归方式）
public void postOrderNR(){
postOrderNR(root);
}
private void postOrderNR(Node node){
if(node==null){
return;
}
Stack<StackNode> stack=new Stack<>();
stack.push(new StackNode(Command.GO,node));
while(!stack.isEmpty()){
StackNode stackNode=stack.pop();
Node n=stackNode.node;
Command command=stackNode.command;
if(command== Command.COUT){
System.out.println(stackNode.node.e);
}else{
stack.push(new StackNode(Command.COUT,n));
if(n.right!=null){
stack.push(new StackNode(Command.GO,n.right));
}
if(n.left!=null){
stack.push(new StackNode(Command.GO,n.left));
}
}
}
}
//枚举命令，GO表示访问元素，COUT表示打印元素
private enum Command{GO,COUT};
private class StackNode{
Command command;
Node node;
StackNode(Command command,Node node){
this.command=command;
this.node=node;
}
}
//BST的层序遍历
public void levelOrder(){
Queue<Node> q=new LinkedList<>();
q.add(root);
while(!q.isEmpty()){
Node node=q.remove();
System.out.println(node.e);
if(node.left!=null){
q.add(node.left);
}
if(node.right!=null){
q.add(node.right);
}
}
}
//寻找BST中的最小元素
public E min(){
if(size==0){
throw new IllegalArgumentException("BST is emmpty");
}
return min(root).e;
}
private Node min(Node node){
if(node.left==null){
return node;
}
return min(node.left);
}
//寻找BST中的最大元素
public E max(){
if(size==0){
throw new IllegalArgumentException("BST is emmpty");
}
return max(root).e;
}
private Node max(Node node){
if(node.right==null){
return node;
}
return max(node.right);
}
//删除BST中的最小值
public E delMin(){
E res=min();
delMin(root);
return res;
}
//删除以node为根结点的BST中的最小值元素
private Node delMin(Node node){
if(node.left==null){
Node nodeRight=node.right;
node.right=null;
size--;
return nodeRight;
}
node.left=delMin(node.left);
return node;
}
//删除BST中的最大值
public E delMax(){
E res=max();
delMax(root);
return res;
}
//删除以node为根结点的BST中的最大值元素
private Node delMax(Node node){
if(node.right==null){
Node nodeLeft=node.left;
node.left=null;
size--;
return nodeLeft;
}
node.right=delMax(node.right);
return node;
}
//删除BST中任意元素
public void del(E e){
root=del(root,e);
}
private Node del(Node node,E e){
if(node==null){
return null;
}
if(e.compareTo(node.e)<0){
return del(node.left,e);
}else if(e.compareTo(node.e)>0){
return del(node.right,e);
}else{
//节点node就是要删除的节点
//该节点只右有子树
if(node.left==null){
Node rightNode=node.right;
node.right=null;
size--;
return rightNode;
}
//该节点只有左子树
if(node.right==null){
Node leftNode=node.left;
node.left=null;
size--;
return leftNode;
}
//删除既有左子树又有右子树的节点
Node s=min(node.right);
s.right=delMin(node.right);
s.left=node.left;
//删除node
node.left=node.right=null;
return s;
}
}
@Override
public String toString() {
StringBuilder res=new StringBuilder();
generateBST(root,0,res);
return res.toString();
}
//生成以node为根节点，深度为depth的描述二叉树的字符串（利用前序遍历）
private void generateBST(Node node,int depth,StringBuilder res){
if(node==null){
res.append(generateDepth(depth)+"null\n");
return;
}
res.append(generateDepth(depth)+node.e+"\n");
generateBST(node.left,depth+1,res);
generateBST(node.right,depth+1,res);
}
private String generateDepth(int depth){
StringBuilder res=new StringBuilder();
for(int i=0;i<depth;i++){
res.append("--");
}
return res.toString();
}
}