Friends Of Appropriate Ages LeetCode solution in C++

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class Solution {
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 public:
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  int numFriendRequests(vector<int> &ages) {
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    sort(ages.begin(), ages.end());
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    int sum = 0;
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    for (int i = ages.size() - 1; i >= 0; i--) {
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      int cutoff = 0.5f * ages[i] + 7;
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      int j = upper_bound(ages.begin(), ages.end(), cutoff) - ages.begin();
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      int k = upper_bound(ages.begin(), ages.end(), ages[i]) - ages.begin();
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      sum += max(0, k - j - 1);
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    }
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    return sum;
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  }
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};