LeetCode-94(Binary Tree Inorder Traversal)

Given a binary tree, return the inorder traversal of its nodes' values.

For example:

Given binary tree 

[1,null,2,3]

,

1
\
2
/
3

return 

[1,3,2]

.

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) {}
* };
*/
class Solution {
public:
vector<int> inorderTraversal(TreeNode* root) {
vector<int> ans;
if(root == NULL) return ans;

if(root->left != NULL){
vector<int> anth = inorderTraversal(root->left);
ans.insert(ans.end(),anth.begin(),anth.end());
}
ans.push_back(root->val);
if(root->right != NULL){
vector<int> anth = inorderTraversal(root->right);
ans.insert(ans.end(),anth.begin(),anth.end());
}
return ans;
}
};