Max Points on a Line

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

Runtime: 40ms

/**
 * Definition for a point.
 * struct Point {
 *     int x;
 *     int y;
 *     Point() : x(0), y(0) {}
 *     Point(int a, int b) : x(a), y(b) {}
 * };
 */
class Solution {
public:
    int maxPoints(vector<Point>& points) {
        int n = points.size();
        if(n <= 2) return n;
        
        int result = 0;
        for(int i = 0; i < points.size(); i++){
            unordered_map<double, int> m;
            m[INT_MIN] = 0;
            m.clear();
            int duplicate = 1;
            for(int j = 0; j < points.size(); j++){
                if(i != j){
                    if(points[i].x == points[j].x && points[i].y == points[j].y)
                        duplicate++;
                    else{
                        double key = (points[i].x == points[j].x ? INT_MAX : (1.0 * (points[i].y - points[j]. y) / (points[i].x - points[j].x)));
                        //m[key] = (m.find(key) == m.end() ? 2 : ++m[key]);
                        m[key]++;
                    }
                }
            }
            if(m.empty()) result = max(result, duplicate);
            else{
                for(unordered_map<double, int>::iterator ite = m.begin(); ite != m.end(); ite++)
                    result = max(result, duplicate + ite->second);
            }
        }
        return result;
    }
};