94. 二叉树的中序遍历

题目链接：https://leetcode.cn/problems/binary-tree-inorder-traversal/

/**
 * 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 walk(TreeNode* node, vector<int> &res) {
        if (!node) {
            return;
        }
        
        if (node->left) {
            walk(node->left, res);
        }
        res.push_back(node->val);
        if (node->right) {
            walk(node->right, res);
        }
    }

    vector<int> inorderTraversal(TreeNode* root) {
        vector<int> res;
        walk(root, res);
        return res;
    }
};

/**

* 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 walk(TreeNode* node, vector<int> &res) {

if (!node) {

return;

}

if (node->left) {

walk(node->left, res);

}

res.push_back(node->val);

if (node->right) {

walk(node->right, res);

}

vector<int> inorderTraversal(TreeNode* root) {

vector<int> res;

walk(root, res);

return res;

}

};