[LeetCode OJ] Max Points on a Line

Max Points on a Line

Submission Details

27 / 27 test cases passed.	Status: Accepted
Runtime: 472 ms	Submitted: 0 minutes ago

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Submitted Code

Language: java

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 /**
  * Definition for a point.
  * class Point {
  *     int x;
  *     int y;
  *     Point() { x = 0; y = 0; }
  *     Point(int a, int b) { x = a; y = b; }
  * }
  */
 import java.util.HashMap;
 import java.util.Map;

 public class Solution {
     public int maxPoints(Point[] points) {
         if (points == null || points.length == 0)
             return 0;
         int N = points.length;
         if (N == 1)
             return 1;
         if (N == 2)
             return 2;

         Map<String, Integer> dict = new HashMap<String, Integer>();
         int maxOverall = 0;
         for (int i = 0; i < N - 1; i++) {
             int same = 1;
             int max = 0;
             for (int j = i + 1; j < N; j++) {

                 int p1x = points[i].x;
                 int p1y = points[i].y;
                 int p2x = points[j].x;
                 int p2y = points[j].y;

                 if (p1x == p2x && p1y == p2y) {
                     same++;
                     continue;
                 }

                 int A = p2y - p1y;
                 int B = p1x - p2x;

                 int GCD = gcd(A, B);
                 if (GCD != 0 && GCD != 1) {
                     A /= GCD;
                     B /= GCD;
                 }
                 if (A < 0) {
                     A = -A;
                     B = -B;
                 }

                 String key = A + "," + B;
 //              System.out.println("round:" + i + " " + key);
                 int value = 1;
                 if (dict.containsKey(key)) {
                     value += dict.get(key);
                 }
                 dict.put(key, value);
                 max = max < value  ? value  : max;
             }

             max += same;
             maxOverall = maxOverall < max ? max : maxOverall;
             dict.clear();
         }

         return maxOverall;
     }

     public int gcd(int a, int b) {
         if (b == 0)
             return a;
         return gcd(b, a % b);
     }
 }
  

 

 

 

 

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