94. Binary Tree Inorder Traversal

迭代方式：

class Solution { public: vector<int> inorderTraversal(TreeNode* root) { vector<int> vt; stack<TreeNode*> st; if(root==NULL) return vt; TreeNode* now=root; while(now!=NULL||!st.empty()) { while(now!=NULL) { st.push(now); now=now->left; } if(!st.empty()) { now=st.top(); st.pop(); vt.push_back(now->val); now=now->right; } } return vt; } };