leetcode ：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]

.

代码：

/**

* 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) {

vector<int> *p_vec=new vector<int>();

preorderTra(root,*p_vec);

return *p_vec;

}

void preorderTra(TreeNode *root,vector<int> & vec){

if(root !=NULL) {

vec.push_back(root->val);

preorderTra(root->left,vec);

preorderTra(root->right,vec);

}

}

};