Lint Code——最多共线的点的个数

/**
 * 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:
    /**
     * @param points an array of point
     * @return an integer
     */
    bool check(map<double,int> &res,double k){
        map<double ,int >::iterator it;
        it=res.find(k);
        if(it==res.end()){
            return false;
        }
        return true;
    }
    void change(map<double,int> &res,double k,int &num){
        
        map<double ,int >::iterator it;
        it=res.find(k);
        it->second++;
        if(it->second>num){
            num=it->second;
        }
    }

    int maxPoints(vector<Point>& points) {
        // Write your code here
        int num=0;
        if(points.size()==0){
            return num;
        }
        num=1;
        
        Point point_i,point_j;
        double k;
        
        for(int i=0;i<points.size();i++){
            point_i=points[i];
            int same=1;
            map<double,int> res;
            map<double ,int >::iterator it;
            for(int j=i+1;j<points.size();j++){
                point_j=points[j];
                if(point_j.x-point_i.x == 0 && point_j.y-point_i.y ==0 ){//同一点
                    same++;
                }else if(point_j.x-point_i.x == 0 && point_j.y-point_i.y !=0){
                    k=(numeric_limits<double>::max)();
                    if(check(res,k)){
                        it=res.find(k);
                        it->second++;
                    }else {
                        res.insert(pair<double,int>(k,1));
                    }
                }else if(point_j.x-point_i.x != 0 ){
                    k=(point_j.y-point_i.y)*1.0/(point_j.x-point_i.x);
                    if(check(res,k)){
                        it=res.find(k);
                        it->second++;
                    }else {
                        res.insert(pair<double,int>(k,1));
                    }
                }
            }
            if(res.empty()){
                if(same>num){
                    num=same;
                }
            }
            for(it=res.begin();it!=res.end();it++){
                if(it->second+same>num){
                    num=it->second+same;
                }
            }
        }
        return num;
    }
};