Add solution #1311

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,222 LeetCode solutions in JavaScript
+# 1,223 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -992,6 +992,7 @@
 1307|[Verbal Arithmetic Puzzle](./solutions/1307-verbal-arithmetic-puzzle.js)|Hard|
 1309|[Decrypt String from Alphabet to Integer Mapping](./solutions/1309-decrypt-string-from-alphabet-to-integer-mapping.js)|Easy|
 1310|[XOR Queries of a Subarray](./solutions/1310-xor-queries-of-a-subarray.js)|Medium|
+1311|[Get Watched Videos by Your Friends](./solutions/1311-get-watched-videos-by-your-friends.js)|Medium|
 1313|[Decompress Run-Length Encoded List](./solutions/1313-decompress-run-length-encoded-list.js)|Easy|
 1317|[Convert Integer to the Sum of Two No-Zero Integers](./solutions/1317-convert-integer-to-the-sum-of-two-no-zero-integers.js)|Easy|
 1318|[Minimum Flips to Make a OR b Equal to c](./solutions/1318-minimum-flips-to-make-a-or-b-equal-to-c.js)|Medium|

solutions/1311-get-watched-videos-by-your-friends.js

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+/**
+ * 1311. Get Watched Videos by Your Friends
+ * https://leetcode.com/problems/get-watched-videos-by-your-friends/
+ * Difficulty: Medium
+ *
+ * There are n people, each person has a unique id between 0 and n-1. Given the arrays watchedVideos
+ * and friends, where watchedVideos[i] and friends[i] contain the list of watched videos and the
+ * list of friends respectively for the person with id = i.
+ *
+ * Level 1 of videos are all watched videos by your friends, level 2 of videos are all watched
+ * videos by the friends of your friends and so on. In general, the level k of videos are all
+ * watched videos by people with the shortest path exactly equal to k with you. Given your id
+ * and the level of videos, return the list of videos ordered by their frequencies (increasing).
+ * For videos with the same frequency order them alphabetically from least to greatest.
+ */
+
+/**
+ * @param {string[][]} watchedVideos
+ * @param {number[][]} friends
+ * @param {number} id
+ * @param {number} level
+ * @return {string[]}
+ */
+var watchedVideosByFriends = function(watchedVideos, friends, id, level) {
+  const visited = new Set([id]);
+  let queue = [id];
+  let currentLevel = 0;
+
+  while (queue.length && currentLevel < level) {
+    const nextQueue = [];
+    queue.forEach(person => friends[person].forEach(friend => {
+      if (!visited.has(friend)) {
+        visited.add(friend);
+        nextQueue.push(friend);
+      }
+    }));
+    queue = nextQueue;
+    currentLevel++;
+  }
+
+  const videoFrequency = new Map();
+  queue.forEach(person => watchedVideos[person].forEach(video => {
+    return videoFrequency.set(video, (videoFrequency.get(video) || 0) + 1);
+  }));
+
+  return [...videoFrequency.entries()]
+    .sort((a, b) => a[1] === b[1] ? a[0].localeCompare(b[0]) : a[1] - b[1])
+    .map(([video]) => video);
+};