【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.

 

1st （7 tries）

class Solution {
public:
    int maxPoints(vector<Point> &points) {
        unordered_map<float,int> kmap;
		int maxres = 0;
		for(int i = 0;i < points.size();i++) {
			int same_num = 1;
			kmap.clear();
			kmap[INT_MIN] = 0;
			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) {
					same_num ++ ;
					continue;
				}
				float k = points[i].x == points[j].x?INT_MAX:(float)(points[j].y - points[i].y)/(points[j].x - points[i].x);  
				kmap[k]++;
			}
			unordered_map<float,int>::iterator iter;
			for(iter = kmap.begin();iter != kmap.end();++iter) {
				if(iter->second+same_num>maxres) {
					maxres = iter->second+same_num;
				}
			}
		}
		return maxres;
    }
};

　　

2nd （ 4 tires）

/**
 * 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 max_p = 0;
        for(unsigned i = 0;i < points.size();i++) {
            map<double,int> slopes;
            int min_p = 0;
            for(unsigned j = 0;j < points.size();j++) {
                if(points[i].x == points[j].x && points[i].y == points[j].y) {
                    min_p++;
                    continue;
                }
                double k = (points[i].x - points[j].x)?( (double)(points[i].y - points[j].y) )/(points[i].x - points[j].x):INT_MAX;
                if(slopes.find(k) == slopes.end())
                    slopes[k] = 1;
                else
                    slopes[k]++;
            }
            if(slopes.size() == 0) {
                if(min_p > max_p)
                    max_p = min_p;
            }
            else {
                for(map<double,int>::iterator iter = slopes.begin();iter != slopes.end();++iter) {
                    if(iter->second + min_p > max_p)
                        max_p = iter->second + min_p;
                }
            }
        }
        return max_p;
    }
};