Max Points on a Line

 

给定二维平面上n个点，找出位于同一条直线上的最大的点的个数。

 

 

/**
 * 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)
    {
        unsigned int size = points.size();
       
        if(size <= 2 )
            return size;
       
           
        std::map<double, int> counter;
        int global_max = 0;
       
        for(int i = 0; i < size -1; ++i)
        {
            int k_infinity = 0;
            int dup = 0;
           
            counter.clear();
           
            for(int j = i + 1; j < size; ++j)
            {
               
                   
                //check same point
                if(points[j].x == points[i].x && points[j].y == points[i].y)
                {
                   
                        dup++;
                       
                    continue;
                }
                  
               
                if(points[j].x == points[i].x)
                {
                   
                       k_infinity++;
                      
                   continue;
                }
                  
                double k = (points[j].y - points[i].y) / (points[j].x - points[i].x);
               
               
                    counter[k]++;
               
            }
           
            int local_max = 0;
            for(auto it = counter.begin(); it != counter.end(); ++it)
            {
                if(it->second > local_max)
                    local_max = it->second;
            }
           
            if(k_infinity > local_max)
                local_max = k_infinity;
           
               
            local_max += dup +1;
           
            if(local_max > global_max)
                global_max = local_max;
           
        }
       
        return global_max;
    }
};