LeetCode题解：Binary Tree Inorder Traversal

Given a binary tree, return the inorder traversal of its nodes’ values.

For example:
Given binary tree {1,#,2,3},
1
\
2
/
3
return [1,3,2].

题意：中序遍历二叉树

解决思路：”左根右“的递归或者通过栈完成的迭代

代码：

public class Solution {
    public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> result = new ArrayList<Integer>();
        Stack<TreeNode> stack = new Stack<TreeNode>();
        TreeNode node = root;

        while(node != null || !stack.isEmpty()){
            while(node != null){
                stack.push(node);
                node = node.left;
            }

            node = stack.pop();
            result.add(node.val);

            node = node.right;
        }

        return result;
    }
}