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
 1 /**
 2  * Definition for a point.
 3  * struct Point {
 4  *     int x;
 5  *     int y;
 6  *     Point() : x(0), y(0) {}
 7  *     Point(int a, int b) : x(a), y(b) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     int maxPoints(vector<Point>& points) {
13         int n = points.size();
14         if(n <= 2) return n;
15         
16         int result = 0;
17         for(int i = 0; i < points.size(); i++){
18             unordered_map<double, int> m;
19             m[INT_MIN] = 0;
20             m.clear();
21             int duplicate = 1;
22             for(int j = 0; j < points.size(); j++){
23                 if(i != j){
24                     if(points[i].x == points[j].x && points[i].y == points[j].y)
25                         duplicate++;
26                     else{
27                         double key = (points[i].x == points[j].x ? INT_MAX : (1.0 * (points[i].y - points[j]. y) / (points[i].x - points[j].x)));
28                         //m[key] = (m.find(key) == m.end() ? 2 : ++m[key]);
29                         m[key]++;
30                     }
31                 }
32             }
33             if(m.empty()) result = max(result, duplicate);
34             else{
35                 for(unordered_map<double, int>::iterator ite = m.begin(); ite != m.end(); ite++)
36                     result = max(result, duplicate + ite->second);
37             }
38         }
39         return result;
40     }
41 };