LeetCode: Max Points on a Line

斜率问题

/**
 * 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) {
        map<double, int> S;
        if (points.size() == 0) return 0;
        int ans = 1;
        for (int i = 0; i < points.size()-1; i++) {
            int num = 1;
            int samep = 0;
            S.clear();
            for (int j = i+1; j < points.size(); j++) {
                double k = numeric_limits<double>::infinity();
                if (points[j].x != points[i].x) k = (double)1.0*(points[j].y-points[i].y)/(points[j].x-points[i].x);
                else if (points[j].y == points[i].y) {samep++; continue;}
                if (S.count(k)) S[k]++;
                else S[k] = 2;
                num = max(num, S[k]);
            }
            ans = max(ans, num+samep);
        }
        return ans;
    }
};

 C#

/**
 * Definition for a point.
 * public class Point {
 *     public int x;
 *     public int y;
 *     public Point() { x = 0; y = 0; }
 *     public Point(int a, int b) { x = a; y = b; }
 * }
 */
public class Solution {
    public int MaxPoints(Point[] points) {
        Dictionary<double, int> S = new Dictionary<double, int>();
        if (points.Length == 0) return 0;
        int ans = 1;
        for (int i = 0; i < points.Length-1; i++) {
            int num = 1;
            int samep = 0;
            S = new Dictionary<double, int>();
            for (int j = i+1; j < points.Length; j++) {
                double k = double.PositiveInfinity;
                if (points[j].x != points[i].x) k = (double)1.0*(points[j].y-points[i].y)/(points[j].x-points[i].x);
                else if (points[j].y == points[i].y) {
                    samep++;
                    continue;
                }
                if (S.ContainsKey(k)) S[k]++;
                else S.Add(k, 2);
                num = Math.Max(num, S[k]);
            }
            ans = Math.Max(ans, num + samep);
        }
        return ans;
    }
}