149.cpp

class Solution {
  // Runtime: 12 ms Your runtime beats 92.52 % of cpp submissions
public:
  int maxPoints(vector<vector<int>> &points) {
    if (points.size() == 0)
      return 0;
    auto getKB = [](int x1, int y1, int x2, int y2) {
      int y = y1 - y2, x = x1 - x2;
      int gcd = __gcd(y, x);
      y = y / gcd, x = x / gcd;
      return (((long long)*reinterpret_cast<unsigned int *>(&y)) << 32ll) |
             (*reinterpret_cast<unsigned int *>(&x));
    };
    int ret = 0;
    for (int i = 0; i < points.size(); ++i) {
      unordered_map<long long, int> hash;
      int duplicate = 0;
      int vertical = 0;
      int res = 0;
      for (int j = 0; j < points.size(); ++j) {
        if (i == j)
          continue;
        else if (points[i][0] == points[j][0] and points[i][1] == points[j][1])
          ++duplicate;
        else if (points[i][0] == points[j][0])
          res = max(res, ++vertical);
        else
          res = max(res, ++hash[getKB(points[i][0], points[i][1], points[j][0],
                                      points[j][1])]);
      }
      ret = max(ret, res + 1 + duplicate);
    }
    return ret;
  }
};