Add solution #2147

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,775 LeetCode solutions in JavaScript
+# 1,776 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1644,6 +1644,7 @@
 2141|[Maximum Running Time of N Computers](./solutions/2141-maximum-running-time-of-n-computers.js)|Hard|
 2144|[Minimum Cost of Buying Candies With Discount](./solutions/2144-minimum-cost-of-buying-candies-with-discount.js)|Easy|
 2145|[Count the Hidden Sequences](./solutions/2145-count-the-hidden-sequences.js)|Medium|
+2147|[Number of Ways to Divide a Long Corridor](./solutions/2147-number-of-ways-to-divide-a-long-corridor.js)|Hard|
 2154|[Keep Multiplying Found Values by Two](./solutions/2154-keep-multiplying-found-values-by-two.js)|Easy|
 2161|[Partition Array According to Given Pivot](./solutions/2161-partition-array-according-to-given-pivot.js)|Medium|
 2176|[Count Equal and Divisible Pairs in an Array](./solutions/2176-count-equal-and-divisible-pairs-in-an-array.js)|Easy|

solutions/2147-number-of-ways-to-divide-a-long-corridor.js

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+/**
+ * 2147. Number of Ways to Divide a Long Corridor
+ * https://leetcode.com/problems/number-of-ways-to-divide-a-long-corridor/
+ * Difficulty: Hard
+ *
+ * Along a long library corridor, there is a line of seats and decorative plants. You are given
+ * a 0-indexed string corridor of length n consisting of letters 'S' and 'P' where each 'S'
+ * represents a seat and each 'P' represents a plant.
+ *
+ * One room divider has already been installed to the left of index 0, and another to the right
+ * of index n - 1. Additional room dividers can be installed. For each position between indices
+ * i - 1 and i (1 <= i <= n - 1), at most one divider can be installed.
+ *
+ * Divide the corridor into non-overlapping sections, where each section has exactly two seats
+ * with any number of plants. There may be multiple ways to perform the division. Two ways are
+ * different if there is a position with a room divider installed in the first way but not in
+ * the second way.
+ *
+ * Return the number of ways to divide the corridor. Since the answer may be very large, return
+ * it modulo 109 + 7. If there is no way, return 0.
+ */
+
+/**
+ * @param {string} corridor
+ * @return {number}
+ */
+var numberOfWays = function(corridor) {
+  const MOD = 1e9 + 7;
+  let seatCount = 0;
+  let result = 1;
+  let lastPairEnd = -1;
+
+  for (let i = 0; i < corridor.length; i++) {
+    if (corridor[i] === 'S') {
+      seatCount++;
+    }
+  }
+  if (seatCount === 0 || seatCount % 2 !== 0) {
+    return 0;
+  }
+
+  seatCount = 0;
+
+  for (let i = 0; i < corridor.length; i++) {
+    if (corridor[i] === 'S') {
+      seatCount++;
+
+      if (seatCount % 2 === 0) {
+        lastPairEnd = i;
+      } else if (seatCount > 1) {
+        const plantsCount = i - lastPairEnd - 1;
+        result = (result * (plantsCount + 1)) % MOD;
+      }
+    }
+  }
+
+  return result;
+};