Max Points on a Line

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.

c++版本：

/** 

 * 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) {  

        // IMPORTANT: Please reset any member data you declared, as  

        // the same Solution instance will be reused for each test case.  

        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;  

    }  

};  

　　java版本：

/**

 * Definition for a point.

 * class Point {

 *     int x;

 *     int y;

 *     Point() { x = 0; y = 0; }

 *     Point(int a, int b) { x = a; y = b; }

 * }

 */

public class Solution{

    public int maxPoints(Point[] points) {

       if(points.length == 0 || points == null) 

            return 0;

       if(points.length == 1)

           return 1;

        int max = 1;

        for(int i = 0; i < points.length; i++){

            int same = 0;

            int localmax = 1;

            HashMap<Float, Integer> fm = new HashMap<Float, Integer>();

            for(int j = 0; j < points.length; j++) {

                if(i == j)

                   continue;

                   

                if(points[i].x == points[j].x && points[i].y == points[j].y) {

                    same ++;

                    continue;

                }

                

                float slop = ((float)(points[i].x - points[j].x)/(points[i].y - points[j].y));

                

                if(fm.containsKey(slop))

                     fm.put(slop, fm.get(slop) + 1);

                else

                    fm.put(slop, 2);

            } 

                for(Integer value : fm.values())

                   localmax = Math.max(localmax, value);

                     

                   localmax += same;

                   max = Math.max(max,localmax);

        }

        return max;

    }

}