二叉树遍历（递归）

package src;

import java.util.Arrays;
import java.util.LinkedList;

public class MyTree {
    private static class TreeNode{
        int data;
        TreeNode leftChild;
        TreeNode rightChild;
        TreeNode(int data){
            this.data=data;
        }
    }
    public static TreeNode createBinaryTree(LinkedList<Integer> inputList){
        TreeNode node=null;
        if(inputList == null || inputList.isEmpty())return null;
        Integer data=inputList.removeFirst();
        if(data != null){
            node=new TreeNode(data);
            node.leftChild = createBinaryTree(inputList);
            node.rightChild=createBinaryTree(inputList);
        }
        return node;
    }
    //前序遍历--根左右
    public static void preOrderTraveral(TreeNode node){
        if(null == node)return;
        System.out.println(node.data);
        preOrderTraveral(node.leftChild);
        preOrderTraveral(node.rightChild);
    }
    //中序遍历 -- 左根右
    public static void inOrderTraveral(TreeNode node){
        if(null == node)return;
        inOrderTraveral(node.leftChild);
        System.out.println(node.data);
        inOrderTraveral(node.rightChild);
    }
    //后序遍历 -- 左右根
    public static void postOrderTraveral(TreeNode node){
        if(null == node)return;
        postOrderTraveral(node.leftChild);
        postOrderTraveral(node.rightChild);
        System.out.println(node.data);
    }

    public static void main(String[] args) {
        LinkedList<Integer> inputList=new LinkedList<Integer>(
                Arrays.asList(new Integer[]{3,2,9,null,null,10,null,null,8,null,4})
        );
        TreeNode node=createBinaryTree(inputList);
        System.out.println("前序遍历:");
        preOrderTraveral(node);
        System.out.println("中序遍历:");
        inOrderTraveral(node);
        System.out.println("后序遍历:");
        postOrderTraveral(node);
    }
}