94.二叉树的中序遍历.java

import java.util.List;
import java.util.Stack;

/*
 * @lc app=leetcode.cn id=94 lang=java
 *
 * [94] 二叉树的中序遍历
 */
/**
 * 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> result = new ArrayList<Integer>();
        if(root == null){
            return result;
        }
        Stack<TreeNode> stack = new Stack<>();

        TreeNode cur = root;
        while(cur != null ||!stack.isEmpty()){
            while(cur!=null){
                stack.push(cur); 
                cur = cur.left;
            }
            cur = stack.pop();
            result.add(cur.val);
            cur = cur.right;
        }
        return result;
    }
}