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.

参考：http://blog.csdn.net/doc_sgl/article/details/17103427

AC的代码：

#include<iostream>
#include<map>
#include<vector>
#include<set>
#include<unordered_map>
#include<climits>
using namespace std;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;}
};int main()
{Solution s;vector<Point> pp= {Point(0,0),Point(0,0),Point(3,10),Point(0,2),Point(0,2),Point(3,10)};cout<<s.maxPoints(pp)<<endl;
}

超时的代码：

#include<iostream>
#include<map>
#include<vector>
#include<set>
using namespace std;struct Point
{int x;int y;Point():x(0),y(0) {}Point(int a,int b):x(a),y(b) {}
};
struct Line
{double k;double t;Line(double a,double b):k(a),t(b) {}
};
bool operator==(const Point &a,const Point &b)
{return a.x==b.x&&a.y==b.y;
}
bool operator<(const Point &a,const Point &b)
{return a.x==b.x?a.y<b.y:a.x<b.x;
}
bool operator==(const Line &a,const Line &b)
{return a.k==b.k&&a.t==b.t;
}
bool operator<(const Line &a,const Line &b)
{return a.k==b.k?a.t<b.t:a.k<b.k;
}
class Solution
{
public:int maxPoints(vector<Point> &points){if(points.empty()||points.size()==1)return points.size();map<Line,set<Point> > mp;int i,j;int count=0;for(i=0; i<(int)points.size()-1; i++){for(j=i+1; j<(int)points.size(); j++){Point x=points[i];Point y=points[j];double k;double t;if(x.x==y.x){k=1e20;t=x.x;}else{k=(y.y-x.y)/(y.x-x.x);t=x.y-x.x*k;}mp[{k,t}].insert(x);mp[{k,t}].insert(y);}}auto start=mp.begin();while(start!=mp.end()){cout<<start->first.k<<" "<<start->first.t<<" "<<start->second.size()<<endl;set<Point> st=start->second;multiset<Point> mul(points.begin(),points.end());auto it=st.begin();int dup=0;while(it!=st.end()){dup+=mul.count(*it)-1;it++;}if(count<(int)st.size()+dup)count=st.size()+dup;start++;}return count;}
};int main()
{Solution s;vector<Point> pp= {Point(0,0),Point(0,0),Point(3,10),Point(0,2),Point(0,2),Point(3,10)};cout<<s.maxPoints(pp)<<endl;
}