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class Solution {
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 public:
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  int thirdMax(vector<int> &nums) {
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    set<int> s;
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    for (int i = 0; i < nums.size(); i++) {
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      s.insert(nums[i]);
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    }
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    if (s.size() >= 3) { // when set size >=3 means 3rd Maximum exist(because
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                         // set does not contain duplicate element)
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      int Third_index_from_last = s.size() - 3;
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      auto third_maximum = next(s.begin(), Third_index_from_last);
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      return *third_maximum;
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    }
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    return *--s.end(); // return maximum if 3rd maximum not exist
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  }
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};