Binary Tree Inorder Traversal

    实现二叉树中序非递归遍历。

/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

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

 * };

 */

vector<int> inorderTraversal(TreeNode *root) 

{

    vector<int> ret;

    stack<TreeNode *> s;

    TreeNode *p = root;

    do

    {

        while (p != NULL)

        {

            s.push(p);

            p = p->left;

        }

        if (!s.empty())

        {

            p = s.top();

            s.pop();

            ret.push_back(p->val);

            p = p->right;

        }

    } while (!s.empty() || p != NULL);

    return ret;

}