目标
实现二叉树的增加、查找、删除、遍历
实现
结点类
public class Node{
int key;
int data;
Node lchild=null;
Node rchild=null;
public Node(int key,int data)
{
this.key=key;
this.data=data;
}
}
二叉树类:
public class BinaryTree {
Node root=null;
public void add(int key,int data)
{
Node node=new Node(key,data);
if (root==null)
root=node;
else
{
Node current=root;
Node pre=null;
while (true)
{
if (key<current.key)
{
pre=current;
current=current.lchild;
if (current==null)
{
pre.lchild=node;
break;
}
}
else
{ pre=current;
current=current.rchild;
if (current==null)
{
pre.rchild=node;
break;
}
}
}
}
}
public Node findNode(int key)
{
Node current=root;
while (current!=null)
{
if (current.key==key)
return current;
else if (key<current.key)
current=current.lchild;
else current=current.rchild;
}
return null;
}
public int findElement(int key)
{
Node current=root;
while (current!=null)
{
if (current.key==key)
return current.data;
else if (key<current.key)
current=current.lchild;
else current=current.rchild;
}
return 0;
}
public boolean delete (int key)
{
Node current=root;
boolean isleftchild=false;
Node parent=root;
Node currentdouble=null;
while (current!=null)
{
if (root.key==key)
{
root=null;
return true;
}
if (current.key==key)
{
//当前结点没有孩子，直接删除
if (current.lchild==null && current.rchild==null)
{
if (isleftchild=true)
parent.lchild=null;
else parent.rchild=null;
return true;
}
//当前结点没有左孩子，有右孩子
if (current.lchild==null && current.rchild!=null)
{
if (isleftchild=true)
parent.lchild=current.rchild;
else parent.rchild=current.lchild;
return true;
}
//当前结点没有右孩子，有左孩子
if (current.lchild!=null && current.rchild==null)
{
if (isleftchild=true)
parent.lchild=current.lchild;
else parent.rchild=current.lchild;
return true;
}
//右孩子，左孩子都有情况，将左孩子结点替换当前结点，当前结点的右孩子作为替换操作后子树中最右的一个结点
if (current.lchild!=null && current.rchild!=null)
{
if (isleftchild=true)
parent.lchild=current.lchild;
else parent.rchild=current.lchild;
currentdouble=current.lchild;
Node rparent=null;
while (currentdouble!=null)
{
rparent=currentdouble;
currentdouble=currentdouble.rchild;
}
rparent.rchild=current.rchild;
return true;
}
}
else if (key<current.key)
{ parent=current;
current=current.lchild;
isleftchild=true;
}
else {
parent=current;
current=current.rchild;
isleftchild=false;
}
}
return false;
}
//先序遍历
public void preorder(Node node)
{
if (node!=null)
{
System.out.println(node.data);
preorder(node.lchild);
preorder(node.rchild);
}
}
//中序遍历
public void midorder(Node node)
{
if (node!=null)
{
midorder(node.lchild);
System.out.println(node.data);
midorder(node.rchild);
}
}
//后序遍历
public void lastorder(Node node)
{
if (node!=null)
{
lastorder(node.lchild);
lastorder(node.rchild);
System.out.println(node.data);
}
}
}
测试类
public class Test {
public static void main(String[] args)
{
BinaryTree bt=new BinaryTree();
bt.add(100, 100);
bt.add(50, 50);
bt.add(150, 150);
bt.add(10, 10);
bt.add(60, 60);
bt.add(120, 120);
bt.add(180, 180);
System.out.println(bt.findElement(50));
System.out.println(bt.root.data);
bt.preorder(bt.root);
System.out.println(bt.root.key);
System.out.println(bt.delete(50));
bt.preorder(bt.root);
}
}