n-ary-tree-preorder-traversal

/*
Runtime: 144 ms, faster than 90.97% of C++ online submissions for N-ary Tree Preorder Traversal.
Memory Usage: 33.2 MB, less than 21.05% of C++ online submissions for N-ary Tree Preorder Traversal.
*/

class Solution {
public:
    vector<int> preorder(Node* root) {
        stack<Node*> q;
        vector<int> res;
        Node *cur;
        if(!root) {
            return res;
        }
        int sz = 1;
        q.push(root);
        while(sz) {
            cur = q.top();
            sz--;
            q.pop();
            for(int i = cur->children.size()-1; i >= 0; i--) {
                q.push(cur->children[i]);
                sz++;
            }
            res.push_back(cur->val);
        }
        return res;
    }
};