刷题——二叉树的中序遍历

双指针法

  void midorder(vector<int>&res, TreeNode* root){if(root == NULL) return;midorder(res, root->left);res.push_back(root->val);midorder(res, root->right);}vector<int> inorderTraversal(TreeNode* root) {// write code herevector<int>res;midorder(res,root);return res;}

入栈法

vector<int> inorderTraversal(TreeNode* root) {// write code herevector<int>res;stack<TreeNode*>s;while(root != NULL || !s.empty()){while(root != NULL){s.push(root);root = root->left;}TreeNode* node =s.top();s.pop();		res.push_back(node->val);//将栈顶元素，添加到数组中root = node->right;}return res;}