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class Solution {
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 public:
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  vector<pair<string, int>> words;
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  string arrangeWords(string text) {
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    // convert to lowercase alphabet
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    text[0] += 32;
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    istringstream iss(text);
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    string word = "";
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    // pos is the index of each word in text.
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    int pos = 0;
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    while (iss >> word) {
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      words.push_back({word, pos});
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      ++pos;
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    }
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    // sort by length and pos.
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    sort(begin(words), end(words),
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         [&](const pair<string, int> &p1, const pair<string, int> &p2) -> bool {
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           if (size(p1.first) == size(p2.first)) return p1.second < p2.second;
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           return size(p1.first) < size(p2.first);
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         });
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    string ans = "";
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    for (auto &x : words) ans += x.first + " ";
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    ans.pop_back();
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    // convert to uppercase alphabet
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    ans[0] -= 32;
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    return ans;
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  }
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};