Add solution #823

Author: JoshCrozier

README.md

@@ -631,6 +631,7 @@
 820|[Short Encoding of Words](./0820-short-encoding-of-words.js)|Medium|
 821|[Shortest Distance to a Character](./0821-shortest-distance-to-a-character.js)|Easy|
 822|[Card Flipping Game](./0822-card-flipping-game.js)|Medium|
+823|[Binary Trees With Factors](./0823-binary-trees-with-factors.js)|Medium|
 824|[Goat Latin](./0824-goat-latin.js)|Easy|
 827|[Making A Large Island](./0827-making-a-large-island.js)|Hard|
 830|[Positions of Large Groups](./0830-positions-of-large-groups.js)|Easy|

solutions/0823-binary-trees-with-factors.js

@@ -0,0 +1,44 @@
+/**
+ * 823. Binary Trees With Factors
+ * https://leetcode.com/problems/binary-trees-with-factors/
+ * Difficulty: Medium
+ *
+ * Given an array of unique integers, arr, where each integer arr[i] is strictly greater than 1.
+ *
+ * We make a binary tree using these integers, and each number may be used for any number of times.
+ * Each non-leaf node's value should be equal to the product of the values of its children.
+ *
+ * Return the number of binary trees we can make. The answer may be too large so return the answer
+ * modulo 109 + 7.
+ */
+
+/**
+ * @param {number[]} arr
+ * @return {number}
+ */
+var numFactoredBinaryTrees = function(arr) {
+  const MOD = 1e9 + 7;
+  const dp = {};
+  const numMap = new Map();
+
+  arr.sort((a, b) => a - b);
+  for (let i = 0; i < arr.length; i++) {
+    numMap.set(arr[i], i);
+  }
+
+  let result = 0;
+  for (let i = 0; i < arr.length; i++) {
+    dp[arr[i]] = 1;
+    for (let j = 0; j < i; j++) {
+      if (arr[i] % arr[j] === 0) {
+        const complement = arr[i] / arr[j];
+        if (numMap.has(complement)) {
+          dp[arr[i]] = (dp[arr[i]] + dp[arr[j]] * dp[complement]) % MOD;
+        }
+      }
+    }
+    result = (result + dp[arr[i]]) % MOD;
+  }
+
+  return result;
+};