Inorder traversal

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

struct Node {
    int data;
    Node* left;
    Node* right;

    Node(int val) {
        data = val;
        left = right = NULL;
    }
};



struct Node {
    int data;
    Node *left;
    Node *right;

    Node(int val) {
        data = val;
        left = right = NULL;
    }
}; 

class Solution {
  public:
    vector<int> v;
    void inorder(Node* root){
        if(root){
            inorder(root->left);
            v.push_back(root->data);
            inorder(root->right);
        }
    }
    vector<int> inOrder(Node* root) {
        inorder(root);
        return v;
    }
};


Node* buildTree(string str) {
    if (str.length() == 0 || str[0] == 'N') return NULL;

    vector<string> ip;

    istringstream iss(str);
    for (string str; iss >> str;) ip.push_back(str);

    Node* root = new Node(stoi(ip[0]));

    queue<Node*> queue;
    queue.push(root);

    int i = 1;
    while (!queue.empty() && i < ip.size()) {

        Node* currNode = queue.front();
        queue.pop();

        string currVal = ip[i];

        if (currVal != "N") {

            currNode->left = new Node(stoi(currVal));

            queue.push(currNode->left);
        }

        i++;
        if (i >= ip.size()) break;
        currVal = ip[i];

        if (currVal != "N") {

            currNode->right = new Node(stoi(currVal));

            queue.push(currNode->right);
        }
        i++;
    }

    return root;
}

int main() {
    int t;
    string tc;
    getline(cin, tc);
    t = stoi(tc);
    while (t--) {
        string s;
        getline(cin, s);
        Node* root = buildTree(s);

        Solution ob;
        vector<int> res = ob.inOrder(root);
        for (int i = 0; i < res.size(); i++) cout << res[i] << " ";
        cout << endl;
    }
    return 0;
}