二叉树
方案一：递归算法
中序遍历顺序左根右
/*** Definition for a binary tree node.* struct TreeNode {* int val;* TreeNode *left;* TreeNode *right;* TreeNode() : val(0), left(nullptr), right(nullptr) {}* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}* };*/
class Solution {
public:void inorder(TreeNode *d,vector<int>&a){//d是当前根节点，a是答案返回数组if(!d){#d为空节点return;}inorder(d->left,a);//左a.push_back(d->val);//根inorder(d->right,a);//右}vector<int> inorderTraversal(TreeNode* root) {vector<int>ans;inorder(root,ans);return ans;}
};