Leetcode 94 Binary Tree Inorder Traversal 二叉树

二叉树的中序遍历，即左子树，根， 右子树

 /**
  * 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 dfs(vector<int> &ans,TreeNode *root){
         if(!root){
             return;
         }
         dfs(ans,root->left);
         ans.push_back(root->val);
         dfs(ans,root->right);
     }
     vector<int> inorderTraversal(TreeNode *root) {
         vector<int> ans;
         dfs(ans,root);
         return ans;
     }
 };