void solve(TreeNode* root, vector&v)
{
if(root==NULL)
{
return;
}
else
{
v.push_back(root->val);
solve(root->left,v);
solve(root->right,v);
}
}
class Solution {
public:
vector preorderTraversal(TreeNode* root) {
vectorv;
solve(root,v);
return v;
}
};```