题目

binary-tree-postorder-traversal

算法

* 直接模拟

代码

class Solution {

public:

    vector<int> postorderTraversal(TreeNode *root) {

        vector<int> res;

        if (!root) return res;

        stack<TreeNode*> s;

        s.push(root);

        TreeNode *head = root;

        while (!s.empty()) {

            TreeNode *top = s.top();

            if ((!top->left && !top->right) || top->left == head || top->right == head) {

                res.push_back(top->val);

                s.pop();

                head = top;

            } else {

                if (top->right) s.push(top->right);

                if (top->left) s.push(top->left);

            }

        }

        return res;

    }

};