leetcode 145. Binary Tree Postorder Traversal

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

For example:
Given binary tree {1,#,2,3},

   1    \     2    /   3

return [3,2,1].

class Solution {public:vector<int> postorderTraversal(TreeNode* root) {vector<int>re;if (root == NULL)return re;vector<pair<TreeNode*,bool>>que;que.push_back(pair<TreeNode*, bool>(root,false));//bool标记节点的右孩子是否进入过队列while (!que.empty()){TreeNode*n = que.back().first;if (!que.back().second){que.back().second = true;if (n->right != NULL)que.push_back(pair<TreeNode*, bool>(n->right, false));if (n->left != NULL)que.push_back(pair<TreeNode*, bool>(n->left,false));if (n->left == NULL&&n->right == NULL){que.pop_back(); re.push_back(n->val);}}else{que.pop_back();re.push_back(n->val);}}return re;}};

accepted