2020-09-23

二叉树前序遍历几种写法

递归

class Solution {
public:
    vector<int> preorderTraversal(TreeNode* root) {
        vector<int> s;
        if(root == NULL){
            return s;
        }
        preorderTraversal(root, s);
        return s;
    }
    void preorderTraversal(TreeNode *root,vector<int> &result){
        if(root == NULL){
            return;
        }
        result.push_back(root->val);
        preorderTraversal(root->left,result);
        preorderTraversal(root->right,result);
    }
};

非递归

park_2048.jpg
Lark20210108-175710.jpeg