N-ary Tree Preorder Traversal LeetCode solution in C++

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class Solution {
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 public:
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  vector<int> preorder(Node *root) {
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    vector<int> ans;
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    stack<Node *> st;
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    st.push(root);
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    while (!st.empty()) {
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      auto frnt = st.top();
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      st.pop();
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      ans.push_back(frnt->val);
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      for (int i = frnt->children.size() - 1; i >= 0; i--) {
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        st.push(frnt->children[i]);
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      }
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    }
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    return ans;
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  }
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};