# Binary Tree Preorder Traversal【144】

Datetime:2016-08-23 01:22:35         Topic: LeetCode          Share        Original >>

### 144. Binary Tree Preorder Traversal

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Total Accepted:  100308 Total Submissions:  262975 Difficulty:  Medium

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]` .

Note: Recursive solution is trivial, could you do it iteratively?

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```/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
//思路首先:递归做法很简单,前序遍历
class Solution {
public:
vector<int> preorderTraversal(TreeNode* root) {
if(root){
result.push_back(root->val);
preorderTraversal(root->left);
preorderTraversal(root->right);
}
return result;
}
private:
vector<int> result;
};```