<p>Given an array of <code>points</code> where <code>points[i] = [x<sub>i</sub>, y<sub>i</sub>]</code> represents a point on the <strong>X-Y</strong> plane, return <em>the maximum number of points that lie on the same straight line</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/25/plane1.jpg" style="width: 300px; height: 294px;" />
<pre>
<strong>Input:</strong> points = [[1,1],[2,2],[3,3]]
<strong>Output:</strong> 3
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/25/plane2.jpg" style="width: 300px; height: 294px;" />
<pre>
<strong>Input:</strong> points = [[1,1],[3,2],[5,3],[4,1],[2,3],[1,4]]
<strong>Output:</strong> 4
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= points.length &lt;= 300</code></li>
	<li><code>points[i].length == 2</code></li>
	<li><code>-10<sup>4</sup> &lt;= x<sub>i</sub>, y<sub>i</sub> &lt;= 10<sup>4</sup></code></li>
	<li>All the <code>points</code> are <strong>unique</strong>.</li>
</ul>

class Solution {
public:
    int maxPoints(vector<vector<int>>& points) {
        if (points.size() == 1) {
            return 1;
        }

        for (int i = 0; i < points.size(); i++) {
            for (int j = i + 1; j < points.size(); j++) {
                std::string h1 = hash1(points[i], points[j]);
                map_[h1].insert(hash2(points[i]));
                map_[h1].insert(hash2(points[j]));
            }
        }

        int res = 0;
        for (auto& [k, v] : map_) {
            // cout << v.size() << "\n";
            res = max(res, static_cast<int>(v.size()));
        }
        return res;
    }

    // for a and b
    string hash1(vector<int>& p1, vector<int>& p2) {
        if (p1[0] == p2[0]) {
            return to_string(p1[0]);
        }

        double a = double(p1[1] - p2[1]) / double(p1[0] - p2[0]);
        double b =
            double(p1[0] * p2[1] - p2[0] * p1[1]) / double(p1[0] - p2[0]);

        string aa = to_string(a);
        aa = aa.substr(0, aa.find(".") + 5);

        string bb = to_string(b);
        bb = bb.substr(0, bb.find(".") + 5);
        // std::cout << aa + "," + bb << "\n";
        return aa + "," + bb;
    }

    // for single point
    string hash2(vector<int>& p) {
        return to_string(p[0]) + "," + to_string(p[1]);
    }

    unordered_map<string, unordered_set<string>> map_;
};
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