只会写递归写法。我太菜了。/** * 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) {} * }; */classSolution{public:voidpreorder(TreeNode*root,vectorintres){//前序遍历辅助函数if(rootnullptr){//空节点返回return;}else{res.push_back(root-val);//把节点的值存入向量preorder(root-left,res);//左递归preorder(root-right,res);//右递归}}vectorintpreorderTraversal(TreeNode*root){//前序遍历入口函数vectorintres;//向量存前序遍历序列preorder(root,res);//调用递归的前序遍历函数returnres;//返回向量}};