[Leetcode]Binary Tree Inorder Traversal

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

和preorder是一样的，把左子节点一直压入到栈中，直到没有左子节点为止，然后出栈访问，存储右子节点。

 1 vector<int> inorderTraversal(TreeNode *root) 
 2 {
 3     vector<int> val;
 4     stack<TreeNode *> path;
 5     TreeNode *p = root;    
 6     while (!path.empty() || p != NULL)
 7     {
 8         while (p != NULL)
 9         {
10             path.push(p);
11             p = p->left;
12         }
13         
14         if (!path.empty())
15         {
16             p = path.top();
17             path.pop();
18             
19             val.push_back(p->val);
20             
21             p = p->right;
22         }
23     } ;
24     
25     return val;
26 }