java實現二叉樹查詢

節點類

/**
 * 節點類
 */
class Node {
    private int id;
    private Node left;
    private Node right;

    /**
     * 前序查詢
     *
     * @param id 需要被尋找的id
     */
    public Node preSearch(int id) {
        // 判斷當前節點
        if (this.id == id) {
            return this;
        }

        Node result = null;
        if (this.left != null) {
            result = this.left.preSearch(id);
        }
        if (result != null) {
            return result;
        }
        if (this.right != null) {
            result = this.right.preSearch(id);
        }
        return result;
    }

    /**
     * 中序查詢
     *
     * @param id 同上
     * @return 找到的節點
     */
    public Node infixSearch(int id) {
        Node result = null;
        if (this.left != null) {
            result = this.left.infixSearch(id);
        }

        if (result != null) {
            return result;
        }

        if (this.id == id) {
            return this;
        }

        if (this.right != null) {
            result = this.right.infixSearch(id);
        }
        return result;
    }

    /**
     * 後序查詢
     *
     * @param id 同上
     * @return
     */
    public Node postSearch(int id) {
        Node result = null;
        if (this.left != null) {
            result = this.left.postSearch(id);
        }
        if (result != null) {
            return result;
        }
        if (this.right != null) {
            result = this.right.postSearch(id);
        }
        if (result != null) {
            return result;
        }
        if (this.id == id) {
            return this;
        }
        return result;
    }

    @Override
    public String toString() {
        return "Node{" +
                "id=" + id +
                '}';
    }

    public Node(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public Node getLeft() {
        return left;
    }

    public void setLeft(Node left) {
        this.left = left;
    }

    public Node getRight() {
        return right;
    }

    public void setRight(Node right) {
        this.right = right;
    }
}
 

二叉樹類

/**
 * 二叉樹
 */
class BinaryTree {
    private Node root;

    /**
     * 前序查詢
     */
    public Node preSearch(int id) {
        if (this.root == null) {
            System.out.println("二叉樹為空");
            return null;
        }
        return this.root.preSearch(id);
    }

    /**
     * 中序查詢
     */
    public Node infixSearch(int id) {
        if (this.root == null) {
            System.out.println("二叉樹為空");
            return null;
        }
        return this.root.infixSearch(id);
    }

    /**
     * 後序查詢
     */
    public Node postSearch(int id) {
        if (this.root == null) {
            System.out.println("二叉樹為空");
            return null;
        }
        return this.root.postSearch(id);
    }

    public void setRoot(Node root) {
        this.root = root;
    }
}
 

測試類

public class SearchDemo {
    public static void main(String[] args) {
        BinaryTree binaryTree = new BinaryTree();
        // 建立需要的節點
        Node root = new Node(000);
        Node node01 = new Node(001);
        Node node02 = new Node(002);
        Node node03 = new Node(003);
        Node node04 = new Node(004);

        // 手動建立二叉樹
        binaryTree.setRoot(root);
        root.setLeft(node01);
        root.setRight(node02);
        node02.setLeft(node03);
        node02.setRight(node04);

        Node node = binaryTree.preSearch(002);
        System.out.println(node);
    }
}