max points on a line

/**
 * Definition for a point.
 * struct Point {
 *     int x;
 *     int y;
 *     Point() : x(0), y(0) {}
 *     Point(int a, int b) : x(a), y(b) {}
 * };
 */
 
 
int maxPoints(vector<Point> &points) {
    unordered_map<double,int>mp;
    int res = 0;
    
    for(int i=0; i<points.size(); i++){
        mp.clear();
        int theSame = 0, vertical = 0, maxSlope = 0;
        for(int j=0; j<points.size(); j++){
            if(points[i].x == points[j].x){
                if(points[i].y == points[j].y){
                    theSame++;//同一个点,没有这个会差1
                }
                else{//垂直
                    vertical++;
                }
            }
            else{
                double slope = (points[j].y-points[i].y)*1.0/(points[j].x-points[i].x);
                mp[slope]++;//计数
                maxSlope = max(maxSlope,mp[slope]);
            }
        }
        
        int maxSingle = max(maxSlope,vertical) + theSame;//单点为基点，最多的点在直线上
        res = max(maxSingle,res);
    }
    
    return res;
}