Update _149.java

src/main/java/com/fishercoder/solutions/_149.java

@@ -1,95 +1,30 @@
-package com.fishercoder.solutions;
+**Updated solution** [credits](https://leetcode.com/problems/max-points-on-a-line/discuss/328269/A-Java-solution-with-my-understanding)
 
-import com.fishercoder.common.classes.Point;
-import java.util.HashMap;
-import java.util.Map;
-
-/**
- * 149. 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.
- *
- * Example 1:
- * Input: [[1,1],[2,2],[3,3]]
- * Output: 3
- * Explanation:
- * ^
- * |
- * |        o
- * |     o
- * |  o
- * +------------->
- * 0  1  2  3  4
- *
- * Example 2:
- * Input: [[1,1],[3,2],[5,3],[4,1],[2,3],[1,4]]
- * Output: 4
- * Explanation:
- * ^
- * |
- * |  o
- * |     o        o
- * |        o
- * |  o        o
- * +------------------->
- * 0  1  2  3  4  5  6
- *
- */
-public class _149 {
-
-  public static class Solution1 {
-    /** credit: https://leetcode.com/problems/max-points-on-a-line/discuss/47113/A-java-solution-with-notes */
-    public int maxPoints(Point[] points) {
-      if (points == null) {
-        return 0;
-      }
-      if (points.length <= 2) {
-        return points.length;
-      }
-
-      Map<Integer, Map<Integer, Integer>> map = new HashMap<>();
-      int result = 0;
-      for (int i = 0; i < points.length; i++) {
-        map.clear();
-        int overlap = 0;
+class Solution {
+    public int maxPoints(int[][] points) {
+        if(points.length < 3)return points.length;
         int max = 0;
-        for (int j = i + 1; j < points.length; j++) {
-          int x = points[j].x - points[i].x;
-          int y = points[j].y - points[i].y;
-          if (x == 0 && y == 0) {
-            overlap++;
-            continue;
-          }
-          int gcd = generateGCD(x, y);
-          if (gcd != 0) {
-            x /= gcd;
-            y /= gcd;
-          }
-
-          if (map.containsKey(x)) {
-            if (map.get(x).containsKey(y)) {
-              map.get(x).put(y, map.get(x).get(y) + 1);
-            } else {
-              map.get(x).put(y, 1);
+        HashMap<Long, Integer> map = new HashMap<Long, Integer>();
+        for(int i = 0;i < points.length;i++) {
+            int dup = 1;
+            map.clear();
+            for(int j = i + 1;j < points.length;j++) {
+                int dx = points[j][0] - points[i][0], dy = points[j][1] - points[i][1];
+                if(dx == 0 && dy == 0)dup++;
+                else {
+                    int gcd = getGcd(dx, dy);
+                    long slope = ((long)(dy / gcd) << 32) + (dx / gcd);
+                    map.put(slope, map.getOrDefault(slope, 0) + 1);
+                }               
             }
-          } else {
-            Map<Integer, Integer> m = new HashMap<>();
-            m.put(y, 1);
-            map.put(x, m);
-          }
-          max = Math.max(max, map.get(x).get(y));
+            max = Math.max(max, dup);
+            for(Map.Entry<Long, Integer> entry : map.entrySet())
+                max = Math.max(max, entry.getValue() + dup);
         }
-        result = Math.max(result, max + overlap + 1);
-      }
-      return result;
+        return max;
     }
-
-    private int generateGCD(int a, int b) {
-      if (b == 0) {
-        return a;
-      } else {
-        return generateGCD(b, a % b);
-      }
+
+    int getGcd(int a, int b) {
+        return b == 0 ? a : getGcd(b, a % b);
     }
-  }
 }