add Java solution for 2001

fishercoder1534 · fishercoder1534 · commit a19e7c7b97a5 · 2021-09-12T09:28:18.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_2001.java b/src/main/java/com/fishercoder/solutions/_2001.java
@@ -22,4 +22,26 @@ public long interchangeableRectangles(int[][] rectangles) {
             return answer;
         }
     }
+
+    public static class Solution2 {
+        /**
+         * credit: https://leetcode.com/problems/number-of-pairs-of-interchangeable-rectangles/discuss/1458404/Java-or-HashMap
+         * <p>
+         * This is an even smarter way to solve this problem:
+         * whenever we encounter a rectangle that has the samw ratio we met before, just increment the answer by the count of this ratio
+         * because this new rectangle could be matched up with all previously encountered ones!
+         * <p>
+         * This is 100% beat on all submissions on space and time as of 9/12/2021.
+         */
+        public long interchangeableRectangles(int[][] rectangles) {
+            Map<Double, Integer> map = new HashMap<>();
+            long ans = 0l;
+            for (int[] rec : rectangles) {
+                double ratio = (double) rec[0] / rec[1];
+                ans += map.getOrDefault(ratio, 0);
+                map.put(ratio, map.getOrDefault(ratio, 0) + 1);
+            }
+            return ans;
+        }
+    }
 }
diff --git a/src/test/java/com/fishercoder/_2001Test.java b/src/test/java/com/fishercoder/_2001Test.java
@@ -9,14 +9,17 @@
 
 public class _2001Test {
     private static _2001.Solution1 solution1;
+    private static _2001.Solution2 solution2;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _2001.Solution1();
+        solution2 = new _2001.Solution2();
     }
 
     @Test
     public void test1() {
         assertEquals(6, solution1.interchangeableRectangles(CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[4,8],[3,6],[10,20],[15,30]")));
+        assertEquals(6, solution2.interchangeableRectangles(CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[4,8],[3,6],[10,20],[15,30]")));
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -9,14 +9,17 @@`
`9`	`9`
`10`	`10`	`public class _2001Test {`
`11`	`11`	`private static _2001.Solution1 solution1;`
	`12`	`+ private static _2001.Solution2 solution2;`
`12`	`13`
`13`	`14`	`@BeforeClass`
`14`	`15`	`public static void setup() {`
`15`	`16`	`solution1 = new _2001.Solution1();`
	`17`	`+ solution2 = new _2001.Solution2();`
`16`	`18`	`}`
`17`	`19`
`18`	`20`	`@Test`
`19`	`21`	`public void test1() {`
`20`	`22`	`assertEquals(6, solution1.interchangeableRectangles(CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[4,8],[3,6],[10,20],[15,30]")));`
	`23`	`+ assertEquals(6, solution2.interchangeableRectangles(CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[4,8],[3,6],[10,20],[15,30]")));`
`21`	`24`	`}`
`22`	`25`	`}`