知识布局-数据结构-搜索二叉树

前言

数据结构是不可避免的。数据结构作为基础知识，在很多面试中都会涉及。所以掌握数据结构可能会给自己的面试成绩加分。今天我编写了一个搜索二叉树。

目录

1.树的节点
2.操作类型
3.树的实现
4.总结

1.树的节点

public class TreeNode {    private int data;    private TreeNode rightNode = null;    private TreeNode leftNode = null;    public int getData() {        return data;    }    public void setData(int data) {        this.data = data;    }    public TreeNode getLeftNode() {        return leftNode;    }    public void setLeftNode(TreeNode leftNode) {        this.leftNode = leftNode;    }    public TreeNode getRightNode() {        return rightNode;    }    public void setRightNode(TreeNode rightNode) {        this.rightNode = rightNode;    }}

2.我们定义一个操作接口

这个操作接口就是我们二叉树支持的操作。支持插入、删除、查找。暂时不支持遍历。

/** * Created by impala on 2017/12/7. */public interface Operator {    public boolean insert(int data);    public TreeNode search(int data);    public boolean delete(int data);}

3.树的实现

/** * Created by impala on 2017/12/7. * * @author forideal */public class BinarySearchTree implements Operator {    private TreeNode rootNode = null;    public BinarySearchTree() {    }    @Override    public boolean insert(int data) {        if (rootNode == null) {            rootNode = new TreeNode();            rootNode.setData(data);        } else {            TreeNode current = rootNode;            while (current != null) {                if (data > current.getData()) {                    if (current.getRightNode() == null) {                        TreeNode rightChild = new TreeNode();                        rightChild.setData(data);                        current.setRightNode(rightChild);                        return true;                    }                    current = current.getRightNode();                } else if (data == current.getData()) {                    System.out.println("The data " + data + " is exist.");                    return false;                } else {                    if (current.getLeftNode() == null) {                        TreeNode leftChild = new TreeNode();                        leftChild.setData(data);                        current.setLeftNode(leftChild);                        return true;                    }                    current = current.getLeftNode();                }            }        }        return true;    }    @Override    public TreeNode search(int data) {        if (rootNode == null) {            System.out.println("The tree is empty.");            return null;        }        TreeNode currentNode = rootNode;        while (currentNode != null) {            if (data > currentNode.getData()) {                currentNode = currentNode.getRightNode();            } else if (data < currentNode.getData()) {                currentNode = currentNode.getLeftNode();            } else {                return currentNode;            }        }        return null;    }    @Override    public boolean delete(int data) {        if (rootNode == null) {            System.out.println("The tree is empty.");            return false;        }        //1.寻找需要删除的节点信息        TreeNode currentNode = rootNode;        TreeNode parentNode = null;        TreeNode targetNode = null;        boolean isParentLeftChildNode = false;        while (currentNode != null) {            if (data > currentNode.getData()) {                parentNode = currentNode;                currentNode = currentNode.getRightNode();                isParentLeftChildNode = false;            } else if (data < currentNode.getData()) {                parentNode = currentNode;                currentNode = currentNode.getLeftNode();                isParentLeftChildNode = true;            } else {                targetNode = currentNode;                break;            }        }        //2.目标删除节点不存在        if (targetNode == null) {            System.out.println("The tree dones't has the data.");            return false;        }        //3.目标删除节点是根节点        if (parentNode == null) {            System.out.println("we will delete root node.");            TreeNode tmpNode = null;            TreeNode leftNode = rootNode.getLeftNode();            TreeNode curNode = rootNode.getRightNode();            while (curNode != null) {                tmpNode = curNode;                curNode = curNode.getLeftNode();                if (curNode == null) {                    tmpNode.setLeftNode(leftNode);                }            }            rootNode = rootNode.getRightNode();            return true;        }        //4.目标删除节点不是跟节点        //4.1.先把target节点的左子节点拼接到右子节点上面        TreeNode leftChildNode = targetNode.getLeftNode();        TreeNode rightChildNode = targetNode.getRightNode();        TreeNode rightCur = rightChildNode;        TreeNode rightParent = null;        while (rightCur != null) {            rightParent = rightCur;            rightCur = rightCur.getLeftNode();            if (rightCur == null) {                rightParent.setLeftNode(leftChildNode);            }        }        //4.2.将刚刚拼接好的节点拼接到之前的树上        if (isParentLeftChildNode) {            //如果相对于父节点来说是左子节点            TreeNode tmpNode = null;            TreeNode curNode = parentNode.getRightNode();            while (curNode != null) {                tmpNode = curNode;                curNode = curNode.getLeftNode();                if (curNode == null) {                    tmpNode.setLeftNode(rightChildNode);                }            }            parentNode.setLeftNode(null);            return true;        } else {            //如果相对于父节点来说是右子节点            parentNode.setRightNode(rightChildNode);            return true;        }    }    public static void main(String[] args) {        BinarySearchTree binarySearchTree = new BinarySearchTree();        binarySearchTree.insert(4);        binarySearchTree.insert(6);        binarySearchTree.insert(4);        binarySearchTree.insert(3);        for (int i = 10; i < 100000; i++) {            binarySearchTree.insert(i);        }        TreeNode node = binarySearchTree.search(3);        if (node == null) {            System.out.println("we don't find 3.");        } else {            System.out.println("we find 3.");        }        binarySearchTree.delete(3);        binarySearchTree.delete(4);        binarySearchTree.delete(6);        node = binarySearchTree.search(3);        if (node == null) {            System.out.println("we don't find 3.");        } else {            System.out.println("we find 3.");        }        node = binarySearchTree.search(4);        if (node == null) {            System.out.println("we don't find 4.");        } else {            System.out.println("we find 4.");        }        node = binarySearchTree.search(6);        if (node == null) {            System.out.println("we don't find 6.");        } else {            System.out.println("we find 6.");        }        binarySearchTree.delete(888);        for (int i = 10; i < 100000; i++) {            node = binarySearchTree.search(i);            if (node == null) {                System.out.println("we don't find " + i + ".");            }        }    }}

4.总结

说句真心话，学习数据结构，最好能够自己动手写一个自己的实现。这样学习的效果会好一些。