此篇文章為我的解題紀錄，程式碼或許並不是很完善

Leetcode - 94. Binary Tree Inorder Traversal

解題思路

使用recursive來遍歷整個數樹，若是有左子樹就一直走，走到無左子樹後開始印出val，再印出當前子樹的root的val後接著再往右子樹走

我滴程式碼

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/**
 * 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:
    vector<int> ans;
    
    vector<int> inorderTraversal(TreeNode* root) {
        
        if (root != NULL)
        {
            inorder(root);
        }
        return ans;
    }
    
    void inorder(TreeNode* root)
    {
        if (root == NULL)
        {
            return;
        }
        else
        {
            inorder(root->left);
            ans.push_back(root->val);
            inorder(root->right);
        }
    }
};