1 /**
2 * Definition for binary tree
3 * struct TreeNode {
4 * int val;
5 * TreeNode *left;
6 * TreeNode *right;
7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {}
8 * };
9 */
10 class Solution {
11 public:
12 vector<int> postorderTraversal(TreeNode *root) {
13 vector<int> res;
14 if(root == NULL)
15 return res;
16 stack<TreeNode*> node;
17 node.push(root);
18 TreeNode* pre, *cur;
19 pre = root;
20 while(!node.empty())
21 {
22 cur = node.top();
23 if(cur->left == pre || cur->right == pre || (cur->left == NULL && cur->right == NULL))
24 {
25 res.push_back(cur->val);
26 node.pop();
27 pre = cur;
28 }
29 else
30 {
31 if(cur->right != NULL)
32 node.push(cur->right);
33
34 if(cur->left != NULL)
35 node.push(cur->left);
36 }
37 }
38 return res;
39 }
40 };
