image.png
递归！！！容易理解！！！
/**
* 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> result;
traverse(root, result);
return result;
}
private:
void traverse(TreeNode* root, vector<int> &ret){
if(root){
traverse(root->left, ret);
ret.push_back(root->val);
traverse(root->right, ret);
}
}
};
迭代：不太好理解：
