Code
#include <bits/stdc++.h>
using namespace std;

// TreeNode structure
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

class Solution {
public:
    // Function to perform iterative Morris
    // preorder traversal of a binary tree
    vector<int> getPreorder(TreeNode* root) {
        // Vector to store the
        // preorder traversal result
        vector<int> preorder;
        
        // Pointer to the current node,
        // starting with the root
        TreeNode* cur = root;

        // Iterate until the
        // current node becomes NULL
        while (cur != NULL) {
            // If the current node
            // has no left child
            if (cur->left == NULL) {
                // Add the value of the
                // current node to the preorder vector
                preorder.push_back(cur->val);
                
                // Move to the right child
                cur = cur->right;
            } else {
                // If the current node has a left child
                // Create a pointer to traverse to the
                // rightmost node in the left subtree
                TreeNode* prev = cur->left;
                
                /