LeetCode: Max Points on a Line

斜率问题

 1 /**

 2  * Definition for a point.

 3  * struct Point {

 4  *     int x;

 5  *     int y;

 6  *     Point() : x(0), y(0) {}

 7  *     Point(int a, int b) : x(a), y(b) {}

 8  * };

 9  */

10 class Solution {

11 public:

12     int maxPoints(vector<Point> &points) {

13         map<double, int> S;

14         if (points.size() == 0) return 0;

15         int ans = 1;

16         for (int i = 0; i < points.size()-1; i++) {

17             int num = 1;

18             int samep = 0;

19             S.clear();

20             for (int j = i+1; j < points.size(); j++) {

21                 double k = numeric_limits<double>::infinity();

22                 if (points[j].x != points[i].x) k = (double)1.0*(points[j].y-points[i].y)/(points[j].x-points[i].x);

23                 else if (points[j].y == points[i].y) {samep++; continue;}

24                 if (S.count(k)) S[k]++;

25                 else S[k] = 2;

26                 num = max(num, S[k]);

27             }

28             ans = max(ans, num+samep);

29         }

30         return ans;

31     }

32 };

 C#

 1 /**

 2  * Definition for a point.

 3  * public class Point {

 4  *     public int x;

 5  *     public int y;

 6  *     public Point() { x = 0; y = 0; }

 7  *     public Point(int a, int b) { x = a; y = b; }

 8  * }

 9  */

10 public class Solution {

11     public int MaxPoints(Point[] points) {

12         Dictionary<double, int> S = new Dictionary<double, int>();

13         if (points.Length == 0) return 0;

14         int ans = 1;

15         for (int i = 0; i < points.Length-1; i++) {

16             int num = 1;

17             int samep = 0;

18             S = new Dictionary<double, int>();

19             for (int j = i+1; j < points.Length; j++) {

20                 double k = double.PositiveInfinity;

21                 if (points[j].x != points[i].x) k = (double)1.0*(points[j].y-points[i].y)/(points[j].x-points[i].x);

22                 else if (points[j].y == points[i].y) {

23                     samep++;

24                     continue;

25                 }

26                 if (S.ContainsKey(k)) S[k]++;

27                 else S.Add(k, 2);

28                 num = Math.Max(num, S[k]);

29             }

30             ans = Math.Max(ans, num + samep);

31         }

32         return ans;

33     }

34 }

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