[LeetCode] 149. Max Points on a Line

思路:
对于每个点, 都建造一个哈希表, key是其他剩下的点跟该点组成的直线的斜率, value是该斜率上的点的记数. 但要记得需要额外的变量记录重复点的个数和垂直于x轴的直线上的点的个数. 这些要特殊记录的.

int maxPoints(vector<Point>& points) {    unordered_map<double, int> m;    int res = 0;    for (int i = 0; i < points.size(); i++) {        int dup = 1;        int vertical = 1;        for (int j = i + 1; j < points.size(); j++) {            Point p1 = points[i];            Point p2 = points[j];            if (p1.x == p2.x) {                if (p1.y == p2.y)                     dup++;                else                    vertical++;            }            else {                double slope = (p2.y - p1.y) * 1.0 / (p2.x - p1.x);                m[slope]++;            }        }        int cur = 0;        for (pair<double, int> p : m)            cur = max(cur, p.second);        res = max(res, cur + dup);        res = max(res, vertical);        m.clear();    }    return res;}