这个二叉树中序遍历为什么会超出时间限制

img


力扣上的题目，显示超出时间限制，是哪里进入死循环了吗，有没有更好的方法


#include <iostream>
#include <vector>
#include <stack>

using namespace std;

//C++实现二叉树中序遍历

struct TreeNode{
    int val;
    TreeNode * left;
    TreeNode * right;
    TreeNode(int x) :
        val(x),
        left(NULL),
        right(NULL){

    }
};

vector<int> inorderTraversal(TreeNode* root) {
    vector<int> res;

    stack<TreeNode *> m_s;
    TreeNode * cur = root;

    while (cur || !m_s.empty())
    {
        for (; cur; cur = cur->left)
        {
            m_s.push(cur);
        }
        cur = m_s.top();

        if (cur)
        {
            res.push_back(cur->val);
            cout << cur->val << ' ';
            m_s.pop();
            cur = cur->right;
        }
    }
    return res;
}

int main()
{
    TreeNode * root = new TreeNode(1);
    TreeNode * tmpr = new TreeNode(2);
    root->right = tmpr;

    TreeNode * tmprl = new TreeNode(3);
    tmpr->left = tmprl;

    //vector<int>::iterator it;
    //vector<int> vc = inorderTraversal(root);
    //for (auto & i : vc)
    //{
    //    cout << i << ' ';
    //}
    //cout << endl;
    inorderTraversal(root);


    system("pause");
    return 0;
}