[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;
}
};