Add solution #2320

JoshCrozier · JoshCrozier · commit 3298f0cc9fb8 · 2025-05-19T19:00:40.000-05:00
diff --git a/README.md b/README.md
@@ -1,4 +1,4 @@
-# 1,882 LeetCode solutions in JavaScript
+# 1,883 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1761,6 +1761,7 @@
 2316|[Count Unreachable Pairs of Nodes in an Undirected Graph](./solutions/2316-count-unreachable-pairs-of-nodes-in-an-undirected-graph.js)|Medium|
 2317|[Maximum XOR After Operations](./solutions/2317-maximum-xor-after-operations.js)|Medium|
 2319|[Check if Matrix Is X-Matrix](./solutions/2319-check-if-matrix-is-x-matrix.js)|Easy|
+2320|[Count Number of Ways to Place Houses](./solutions/2320-count-number-of-ways-to-place-houses.js)|Medium|
 2336|[Smallest Number in Infinite Set](./solutions/2336-smallest-number-in-infinite-set.js)|Medium|
 2338|[Count the Number of Ideal Arrays](./solutions/2338-count-the-number-of-ideal-arrays.js)|Hard|
 2342|[Max Sum of a Pair With Equal Sum of Digits](./solutions/2342-max-sum-of-a-pair-with-equal-sum-of-digits.js)|Medium|
diff --git a/solutions/2320-count-number-of-ways-to-place-houses.js b/solutions/2320-count-number-of-ways-to-place-houses.js
@@ -0,0 +1,34 @@
+/**
+ * 2320. Count Number of Ways to Place Houses
+ * https://leetcode.com/problems/count-number-of-ways-to-place-houses/
+ * Difficulty: Medium
+ *
+ * There is a street with n * 2 plots, where there are n plots on each side of the street. The plots
+ * on each side are numbered from 1 to n. On each plot, a house can be placed.
+ *
+ * Return the number of ways houses can be placed such that no two houses are adjacent to each other
+ * on the same side of the street. Since the answer may be very large, return it modulo 109 + 7.
+ *
+ * Note that if a house is placed on the ith plot on one side of the street, a house can also be
+ * placed on the ith plot on the other side of the street.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var countHousePlacements = function(n) {
+  const MOD = 1e9 + 7;
+  let empty = 1n;
+  let house = 1n;
+
+  for (let i = 2; i <= n; i++) {
+    const nextEmpty = (empty + house) % BigInt(MOD);
+    const nextHouse = empty;
+    empty = nextEmpty;
+    house = nextHouse;
+  }
+
+  const sideWays = (empty + house) % BigInt(MOD);
+  return Number((sideWays * sideWays) % BigInt(MOD));
+};
