【LeetCode】Binary Tree Preorder Traversal

/** * 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> preorderTraversal(TreeNode *root) {        stack<TreeNode*>node;vector<int> result;TreeNode *temp;temp = root;while (temp || node.size()){while (temp){node.push(temp);result.push_back(temp->val);temp = temp->left;}if (node.size()){temp = node.top();node.pop();temp = temp->right;}}return result;    }};