# Description

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].

The original problem is here.

The original code is here.

# My Solution

I solve this problem in C++, as below:

``````/*
*Binary Tree Preorder Traversal
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<stack>
#include<vector>
#include<stdlib.h>
using namespace std;

/**
* Definition for a binary tree node.
* 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) {
vector<int> vec;
stack<TreeNode*> myStack;
TreeNode * node;
if(root != NULL)
myStack.push(root);
while(!myStack.empty()){
node = myStack.top();
vec.push_back(node->val);
myStack.pop();
if(node->right!=NULL)
myStack.push(node->right);
if(node->left!=NULL)
myStack.push(node->left);
}
return vec;

}
};
``````

# Note

A stack is needed for traversal the tree iteratively.