Maximum Number of Visible Points LeetCode solution in C++

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class Solution {
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 public:
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  int visiblePoints(vector<vector<int>> &points, int angle, vector<int> &location) {
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    vector<double> pa;
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    int at_start = 0;
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    for (auto point : points) {
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      if (point[0] == location[0] && point[1] == location[1])
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        at_start++;
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      else {
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        double ang = atan2(point[1] - location[1], point[0] - location[0]) * 180.0 / M_PI;
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        if (ang < 0) ang += 360;
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        pa.push_back(ang);
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      }
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    }
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    sort(pa.begin(), pa.end());
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    int n = pa.size();
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    int l = 0, ret = 0;
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    for (int i = 0; i < n; i++) pa.push_back(pa[i] + 360);
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    for (int r = 0; r < pa.size(); r++) {
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      while ((pa[r] - pa[l]) > angle) l++;
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      ret = max(ret, r - l + 1);
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    }
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    return ret + at_start;
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  }
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};