94. 二叉树的中序遍历

中序递归&&非递归
递归方法：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> rev = new ArrayList<Integer>();

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

非递归方法：

public class Solution {
    public List < Integer > inorderTraversal(TreeNode root) {
        List < Integer > res = new ArrayList < > ();
        Stack < TreeNode > stack = new Stack < > ();
        TreeNode curr = root;
        while (curr != null || !stack.isEmpty()) {
            while (curr != null) {
                stack.push(curr);
                curr = curr.left;
            }
            curr = stack.pop();
            res.add(curr.val);
            curr = curr.right;
        }
        return res;
    }
}

来源：CSDN

作者：Haha@25

链接：https://blog.csdn.net/qq_37637619/article/details/103794135