Binary Tree Preorder Traversal

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

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

   1
    \
     2
    /
   3

return [1,2,3].

解题思路:先序遍历较为简单，直接按顺序存栈即可.

#include<iostream>
#include<vector>
#include<stack>
using namespace std;

struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(NULL), right(NULL) {}

};
//先序遍历
vector<int> preorderTraversal(TreeNode *root) {
	vector<int>ResultVectorPsotorder;
	stack<TreeNode*>StackNode;
	if (root == NULL)
		return ResultVectorPsotorder;
	StackNode.push(root);
	TreeNode*CurNode = NULL;
	while (!StackNode.empty())
	{
		CurNode = StackNode.top();
		ResultVectorPsotorder.push_back(CurNode->val);
		StackNode.pop();
		if (CurNode->right)
			StackNode.push(CurNode->right);
		if (CurNode->left)
			StackNode.push(CurNode->left);
	}
	return ResultVectorPsotorder;
}