LintCode66

二叉树的前序遍历

给出一棵二叉树 

{1,#,2,3}

,

1
\
2
/
3

 返回 

[1,2,3]

代码：/**

 * Definition of TreeNode:

 * class TreeNode {

 * public:

 *     int val;

 *     TreeNode *left, *right;

 *     TreeNode(int val) {

 *         this->val = val;

 *         this->left = this->right = NULL;

 *     }

 * }

 */

 

class Solution {

public:

    vector<int> preorderTraversal(TreeNode *root) {

     preTraversal(root);

     return v;

    }

private:

    vector<int > v;    

    void preTraversal(TreeNode *root){

        if(root==NULL)

            return;

        v.push_back(root->val);

        preTraversal(root->left);

        

        preTraversal(root->right);

    }

};

 .