LeetCode之旅（32）

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].

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    vector<int> postorderTraversal(TreeNode *root) {        vector<int> res;        if (!root) return res;        stack<TreeNode *> s;        TreeNode *p = root;        s.push(p);        while (!s.empty()) {            TreeNode *cur = s.top();            if (cur->right==p || cur->left==p || (!cur->left && !cur->right)) {                s.pop();                res.push_back(cur->val);                p = cur;            } else {                if (cur->right) s.push(cur->right);                if (cur->left) s.push(cur->left);            }        }        return res;    }};