solution.cpp

/**
 * 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) 
    {
        unordered_map<float,int> mp;
        int maxNum = 0;
        for(int i = 0; i < points.size(); i++)
        {
            mp.clear();
            mp[INT_MIN] = 0;
            int duplicate = 1;
            for(int j = 0; j < points.size(); j++)
            {
                if(j == i) continue;
                if(points[i].x == points[j].x && points[i].y == points[j].y)
                {
                    duplicate++;
                    continue;
                }
                float k = points[i].x == points[j].x ? INT_MAX : (float)(points[j].y - points[i].y)/(points[j].x - points[i].x);
                mp[k]++;
            }
            unordered_map<float, int>::iterator it = mp.begin();
            for(; it != mp.end(); it++)
                if(it->second + duplicate > maxNum)
                    maxNum = it->second + duplicate;
        }
        return maxNum;
    }
};