Inorder Traversal (Iterative)

void inOrder(Node *root) {
        stack<Node*>S;
        Node* curr = root;
        vector<int>ans;
        while(curr!=nullptr or !S.empty())
        {
            while(curr)
            {
                S.push(curr);
                curr = curr->left;
            }
            curr = S.top();
            S.pop();
            ans.push_back(curr->data);
            curr = curr->right;
        }
        for(int i=0 ; i<ans.size() ; i++)   cout<<ans[i]<<" ";
    }