Add solution #720

Author: JoshCrozier

README.md

@@ -301,6 +301,7 @@
 705|[Design HashSet](./0705-design-hashset.js)|Easy|
 706|[Design HashMap](./0706-design-hashmap.js)|Easy|
 713|[Subarray Product Less Than K](./0713-subarray-product-less-than-k.js)|Medium|
+720|[Longest Word in Dictionary](./0720-longest-word-in-dictionary.js)|Medium|
 722|[Remove Comments](./0722-remove-comments.js)|Medium|
 724|[Find Pivot Index](./0724-find-pivot-index.js)|Easy|
 733|[Flood Fill](./0733-flood-fill.js)|Easy|

solutions/0720-longest-word-in-dictionary.js

@@ -0,0 +1,32 @@
+/**
+ * 720. Longest Word in Dictionary
+ * https://leetcode.com/problems/longest-word-in-dictionary/
+ * Difficulty: Medium
+ *
+ * Given an array of strings words representing an English Dictionary, return the longest word
+ * in words that can be built one character at a time by other words in words.
+ *
+ * If there is more than one possible answer, return the longest word with the smallest
+ * lexicographical order. If there is no answer, return the empty string.
+ *
+ * Note that the word should be built from left to right with each additional character being
+ * added to the end of a previous word.
+ */
+
+/**
+ * @param {string[]} words
+ * @return {string}
+ */
+var longestWord = function(words) {
+  const set = new Set();
+  let result = '';
+
+  words.sort().forEach(word => {
+    if (word.length === 1 || set.has(word.slice(0, -1))) {
+      set.add(word);
+      result = word.length > result.length ? word : result;
+    }
+  });
+
+  return result;
+};