题解 | #二叉树的中序遍历#

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
     */
    public int[] inorderTraversal (TreeNode root) { // 中序遍历
        // write code here
         int[] order = new int[1001];
        doInorderTraversal(root, order);
         return Arrays.copyOfRange(order, 0, orderIndex);
    }
    
     static int orderIndex = 0;

    private static void doInorderTraversal(TreeNode root, int[] order) {
        if (root == null) {
            return;
        }
        doInorderTraversal(root.left, order);
        order[orderIndex++] = root.val;
        doInorderTraversal(root.right, order);
    }
}