【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;
    }
};