Add solution #1434

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,301 LeetCode solutions in JavaScript
+# 1,302 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1094,6 +1094,7 @@
 1431|[Kids With the Greatest Number of Candies](./solutions/1431-kids-with-the-greatest-number-of-candies.js)|Easy|
 1432|[Max Difference You Can Get From Changing an Integer](./solutions/1432-max-difference-you-can-get-from-changing-an-integer.js)|Medium|
 1433|[Check If a String Can Break Another String](./solutions/1433-check-if-a-string-can-break-another-string.js)|Medium|
+1434|[Number of Ways to Wear Different Hats to Each Other](./solutions/1434-number-of-ways-to-wear-different-hats-to-each-other.js)|Hard|
 1436|[Destination City](./solutions/1436-destination-city.js)|Easy|
 1437|[Check If All 1's Are at Least Length K Places Away](./solutions/1437-check-if-all-1s-are-at-least-length-k-places-away.js)|Easy|
 1443|[Minimum Time to Collect All Apples in a Tree](./solutions/1443-minimum-time-to-collect-all-apples-in-a-tree.js)|Medium|

solutions/1434-number-of-ways-to-wear-different-hats-to-each-other.js

@@ -0,0 +1,53 @@
+/**
+ * 1434. Number of Ways to Wear Different Hats to Each Other
+ * https://leetcode.com/problems/number-of-ways-to-wear-different-hats-to-each-other/
+ * Difficulty: Hard
+ *
+ * There are n people and 40 types of hats labeled from 1 to 40.
+ *
+ * Given a 2D integer array hats, where hats[i] is a list of all hats preferred by the ith person.
+ *
+ * Return the number of ways that n people can wear different hats from each other.
+ *
+ * Since the answer may be too large, return it modulo 109 + 7.
+ */
+
+/**
+ * @param {number[][]} hats
+ * @return {number}
+ */
+var numberWays = function(hats) {
+  const MOD = 1e9 + 7;
+  const hatToPeople = Array(41).fill().map(() => []);
+  const cache = new Map();
+
+  for (let person = 0; person < hats.length; person++) {
+    for (const hat of hats[person]) {
+      hatToPeople[hat].push(person);
+    }
+  }
+
+  function assignHats(hat, usedMask) {
+    if (hat > 40) {
+      return usedMask === (1 << hats.length) - 1 ? 1 : 0;
+    }
+
+    const key = `${hat}:${usedMask}`;
+    if (cache.has(key)) {
+      return cache.get(key);
+    }
+
+    let ways = assignHats(hat + 1, usedMask);
+
+    for (const person of hatToPeople[hat]) {
+      if (!(usedMask & (1 << person))) {
+        ways = (ways + assignHats(hat + 1, usedMask | (1 << person))) % MOD;
+      }
+    }
+
+    cache.set(key, ways);
+    return ways;
+  }
+
+  return assignHats(1, 0);
+};