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) {
        List<Integer> list=new ArrayList<>();
        inorder(root,list);
        Object[] a=list.toArray();
        Integer[] aa=new Integer[a.length];
        // for(int i=0;i<a.length;i++){
        //     aa[i]=(Integer)(a[i]);
        // }
        int[] aaa;
        aa=list.toArray(new Integer[0]);
        aaa=Arrays.stream(aa).mapToInt(Integer::valueOf).toArray(); 
        return aaa;

   
    }
    public void inorder(TreeNode root,List<Integer> list){
        if(root==null){
            return;
        }
        inorder(root.left,list);
        list.add(root.val);
        inorder(root.right,list);
    }
}