Find a Value of a Mysterious Function Closest to Target LeetCode solution in C++

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class Solution {
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 public:
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  int closestToTarget(vector<int> &arr, int target) {
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    vector<int> q;
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    q.reserve(32);
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    int best = 1'000'000'000;
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    for (size_t i = 0; i < arr.size(); i++) {
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      for (auto &x : q) x &= arr[i];
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      q.push_back(arr[i]);
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      q.erase(unique(begin(q), end(q)), end(q));
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      for (auto x : q) best = min(best, abs(target - x));
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    }
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    return best;
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  }
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};