[LeetCode]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.

思考：考虑以下几种情况：

1.points中0、1、2个点；

2.points含相同点如{[0,0],[0,0]}，{[1,1],[1,1]，[2,2],[2,2]}};

3.斜率为无穷。

 

/**
 * 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) {
        int n=points.size(); //point个数
        if(n<=2) return n;
        int i,j;
        int max=0;
        map<double,int> m; //每个point斜率集合
        for(i=0;i<n;i++)
        {
            m.clear();
			m[INT_MAX]=0; //斜率为无穷
			int samepoint=1; //相同点个数
            for(j=0;j<n;j++)
            {
				if(i==j) continue;
				if((points[j].x==points[i].x)&&(points[j].y==points[i].y)) samepoint++;
                else if(points[j].x==points[i].x) m[INT_MAX]++;
                else
                {
                    double k=(double)(points[j].y-points[i].y)/(points[j].x-points[i].x); //斜率不为无穷	
                    if(m.find(k)==m.end()) m[k]=1;
					else m[k]++;
                }
            }
			map<double,int>::iterator iter;
			for(iter=m.begin();iter!=m.end();iter++)
			{
			//	cout<<iter->first<<" "<<iter->second+samepoint<<endl;
				if(iter->second+samepoint>max) max=iter->second+samepoint;
			}
        }
        return max;
    }
};