[LeetCode]Binary Tree Preorder Traversal

原题链接：http://oj.leetcode.com/problems/binary-tree-preorder-traversal/

题意描述：

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?

题解：

　　裸的二叉树遍历，没什么好说的。另外，关于二叉树，我之前做了一个还算详细的总结，这里给出链接：http://www.cnblogs.com/codershell/p/3291601.html

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void traversal(vector<int>& v,TreeNode *root){
        if(root==NULL) return;
        v.push_back(root->val);
        traversal(v,root->left);
        traversal(v,root->right);
    }
    vector<int> preorderTraversal(TreeNode *root) {
        vector<int> v;
        
        traversal(v,root);
        
        return v;
    }
};