/**  
         * 在二叉树中搜索某个元素  
         *  
         * @className: FindInBinaryTreeUsingRecursion  
         * @author: Max Solider  
         * @date: 2023-06-11 15:37  
         */public class FindInBinaryTreeUsingRecursion {  

            public static BinaryTreeNode findInBinaryTreeUsingRecursion(BinaryTreeNode root, int k) {  
                if (root == null) {  
                    return null;  
                }  
                if (root.getData() == k) {  
                    return root;  
                }  
                BinaryTreeNode result = findInBinaryTreeUsingRecursion(root.getLeft(), k);  
                if (result != null) {  
                    return result;  
                }  
                result = findInBinaryTreeUsingRecursion(root.getRight(), k);  
                if (result != null) {  
                    return result;  
                }  
                return null;  
            }  

            public static void main(String[] args) {  
                BinaryTreeNode node4 = new BinaryTreeNode(4, null, null);  
                BinaryTreeNode node5 = new BinaryTreeNode(5, null, null);  
                BinaryTreeNode node6 = new BinaryTreeNode(6, null, null);  
                BinaryTreeNode node7 = new BinaryTreeNode(7, null, null);  
                BinaryTreeNode node2 = new BinaryTreeNode(2, node4, node5);  
                BinaryTreeNode node3 = new BinaryTreeNode(3, node6, node7);  
                BinaryTreeNode node1 = new BinaryTreeNode(1, node2, node3);  
                System.out.println(findInBinaryTreeUsingRecursion(node1, 10));  
                System.out.println(findInBinaryTreeUsingRecursion(node1, 5));  
            }  
        }