Leetcode Binary Tree&n…

    vector<<span style="color:blue">int> preorderTraversal(TreeNode *root) {

        vector<<span style="color:blue">int> val_vector;

        std::stack<<span style="color:blue">TreeNode*> my_stack;

 

        while (root||!my_stack.empty())

        {

            if(root){

                my_stack.push(root);

                val_vector.push_back(root->val);

                root=root->left;

            }

            else{

                root=my_stack.top();

                root=root->right;

                my_stack.pop();

            }

        }

        return val_vector;

    }