add 823

fishercoder1534 · fishercoder1534 · commit 855ada5caba6 · 2021-03-13T15:57:04.000-08:00
diff --git a/README.md b/README.md
@@ -426,7 +426,8 @@ _If you like this project, please leave me a star._ &#9733;
 |836|[Rectangle Overlap](https://leetcode.com/problems/rectangle-overlap/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_836.java) | [:tv:](https://youtu.be/o6hHUk4DOW0) |Easy|
 |832|[Flipping an Image](https://leetcode.com/problems/flipping-an-image/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_832.java) |  |Easy|
 |830|[Positions of Large Groups](https://leetcode.com/problems/positions-of-large-groups/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_830.java) |  |Easy|
-|824|[Goat Latin](https://leetcode.com/problems/goat-latin/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_824.java) |  |Easy| 
+|824|[Goat Latin](https://leetcode.com/problems/goat-latin/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_824.java) |  |Easy|
+|823|[Binary Trees With Factors](https://leetcode.com/problems/binary-trees-with-factors/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_823.java) |  |Medium|
 |821|[Shortest Distance to a Character](https://leetcode.com/problems/shortest-distance-to-a-character/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_821.java) |  |Easy|
 |820|[Short Encoding of Words](https://leetcode.com/problems/short-encoding-of-words/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_820.java) |  |Medium|
 |819|[Most Common Word](https://leetcode.com/problems/most-common-word/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_819.java) |  |Easy| HashMap
diff --git a/src/main/java/com/fishercoder/solutions/_823.java b/src/main/java/com/fishercoder/solutions/_823.java
@@ -0,0 +1,35 @@
+package com.fishercoder.solutions;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+public class _823 {
+    public static class Solution1 {
+        /**
+         * credit: https://leetcode.com/problems/binary-trees-with-factors/discuss/126277/Concise-Java-solution-using-HashMap-with-detailed-explanation.-Easily-understand!!!
+         */
+        long MOD = 1000000007l;
+
+        public int numFactoredBinaryTrees(int[] arr) {
+            Arrays.sort(arr);
+            Map<Integer, Long> map = new HashMap<>();
+            long count = 1;
+            map.put(arr[0], count);
+            for (int i = 1; i < arr.length; i++) {
+                count = 1;
+                for (int key : map.keySet()) {
+                    if (arr[i] % key == 0 && map.containsKey(arr[i] / key)) {
+                        count += map.get(key) * map.get(arr[i] / key);
+                    }
+                }
+                map.put(arr[i], count);
+            }
+            long sum = 0;
+            for (int key : map.keySet()) {
+                sum = (sum + map.get(key)) % MOD;
+            }
+            return (int) sum;
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_823Test.java b/src/test/java/com/fishercoder/_823Test.java
@@ -0,0 +1,32 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._823;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _823Test {
+    private static _823.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _823.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(3, solution1.numFactoredBinaryTrees(new int[]{2, 4}));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals(9, solution1.numFactoredBinaryTrees(new int[]{2, 3, 4, 6, 9}));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals(25, solution1.numFactoredBinaryTrees(new int[]{2, 3, 4, 8, 16, 18}));
+    }
+
+}
