题解 | #农场牛的最佳观赏次序#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型一维数组
     */
    List<Integer> list = new LinkedList<>();
    public int[] inorderTraversal (TreeNode root) {
        traveser(root);
	  //结果集封装
        int[] res = new int[list.size()];
        for(int i =0;i<list.size();i++){
            res[i] = list.get(i);
        }
        return res;
    }
  //中序遍历
    void traveser(TreeNode root){
        if(root == null) return ;
        traveser(root.left);
        list.add(root.val);
        traveser(root.right);
    }
}