Add solution #953

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,038 LeetCode solutions in JavaScript
+# 1,039 LeetCode solutions in JavaScript
 
 [https://leetcode.com/](https://leetcode.com/)
 
@@ -762,6 +762,7 @@
 950|[Reveal Cards In Increasing Order](./solutions/0950-reveal-cards-in-increasing-order.js)|Medium|
 951|[Flip Equivalent Binary Trees](./solutions/0951-flip-equivalent-binary-trees.js)|Medium|
 952|[Largest Component Size by Common Factor](./solutions/0952-largest-component-size-by-common-factor.js)|Hard|
+953|[Verifying an Alien Dictionary](./solutions/0953-verifying-an-alien-dictionary.js)|Easy|
 966|[Vowel Spellchecker](./solutions/0966-vowel-spellchecker.js)|Medium|
 970|[Powerful Integers](./solutions/0970-powerful-integers.js)|Easy|
 976|[Largest Perimeter Triangle](./solutions/0976-largest-perimeter-triangle.js)|Easy|

solutions/0953-verifying-an-alien-dictionary.js

@@ -0,0 +1,37 @@
+/**
+ * 953. Verifying an Alien Dictionary
+ * https://leetcode.com/problems/verifying-an-alien-dictionary/
+ * Difficulty: Easy
+ *
+ * In an alien language, surprisingly, they also use English lowercase letters, but possibly
+ * in a different order. The order of the alphabet is some permutation of lowercase letters.
+ *
+ * Given a sequence of words written in the alien language, and the order of the alphabet,
+ * return true if and only if the given words are sorted lexicographically in this alien language.
+ */
+
+/**
+ * @param {string[]} words
+ * @param {string} order
+ * @return {boolean}
+ */
+var isAlienSorted = function(words, order) {
+  const map = new Map(order.split('').map((char, index) => [char, index]));
+
+  for (let i = 0; i < words.length - 1; i++) {
+    if (!helper(words[i], words[i + 1])) return false;
+  }
+
+  return true;
+
+  function helper(word1, word2) {
+    for (let i = 0; i < word1.length; i++) {
+      if (i >= word2.length) return false;
+      const char1 = map.get(word1[i]);
+      const char2 = map.get(word2[i]);
+      if (char1 < char2) return true;
+      if (char1 > char2) return false;
+    }
+    return true;
+  }
+};