二叉排序树

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class tree {

	public static void main(String[] args) throws NumberFormatException, IOException {
		// TODO Auto-generated method stub
		BufferedReader reader = new BufferedReader(
				new InputStreamReader(System.in));
		String line;
		while ((line=reader.readLine()) != null) {
			//readLine()每次读回来的都是一行
			int n = Integer.parseInt(line);
			//parseInt(String s): 返回用十进制参数表示的整数值
			String[] vals = reader.readLine().split(" ");
			Node tree = null;
			for (int i=0; i< n; i++) {
				int x = Integer.parseInt(vals[i]);
				tree = insert(tree, x);
			}

			preOrder(tree);
			System.out.println();
			inOrder(tree);
			System.out.println();
			postOrder(tree);
			System.out.println();
		}
	}
	
	//一个递归函数用来插入数
	static Node insert(Node root, int x) {
		if (root == null) {
			root = new Node(x);
			return root;
		} else if (x < root.val) {
			root.left = insert(root.left, x);
		} else if (x > root.val) {
			root.right = insert(root.right, x);
		}
		// 忽略数值相等的结点
		return root;
	}

	// 前序遍历
	static void preOrder(Node root) {
		if (root != null)
			System.out.print(root.val+" ");
		if (root.left != null) preOrder(root.left);
		if (root.right != null) preOrder(root.right);
	}

	// 中序遍历
	static void inOrder(Node root) {
		if (root.left != null) inOrder(root.left);
		if (root != null)
			System.out.print(root.val+" ");
		if (root.right != null) inOrder(root.right);
	}

	// 后序遍历
	static void postOrder(Node root) {
		if (root.left != null) postOrder(root.left);
		if (root.right != null) postOrder(root.right);
		if (root != null)
			System.out.print(root.val+" ");
	}

}
class Node {
	Node left;
	Node right;
	int val;
	Node(int val) {
		this.val = val;
	}
}