LeetCode-94 Binary Tree Inorder Traversal Solution (with Java)

1. Description: 

Notes: 

2. Examples: 

3.Solutions:

/**
 * Created by sheepcore on 2019-05-09
 * 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) {
        Stack<TreeNode> stack = new Stack<TreeNode>();
        List<Integer> res = new ArrayList<>();
        while (root != null || !stack.isEmpty()){
            while (root != null) {
                stack.push(root);
                root = root.left;
            }
            root = stack.pop();
            res.add(root.val);
            root = root.right;
        }
        return res;
    }
}