Add solution #809

Author: JoshCrozier

README.md

@@ -617,6 +617,7 @@
 805|[Split Array With Same Average](./0805-split-array-with-same-average.js)|Hard|
 806|[Number of Lines To Write String](./0806-number-of-lines-to-write-string.js)|Easy|
 808|[Soup Servings](./0808-soup-servings.js)|Medium|
+809|[Expressive Words](./0809-expressive-words.js)|Medium|
 819|[Most Common Word](./0819-most-common-word.js)|Easy|
 821|[Shortest Distance to a Character](./0821-shortest-distance-to-a-character.js)|Easy|
 824|[Goat Latin](./0824-goat-latin.js)|Easy|

solutions/0809-expressive-words.js

@@ -0,0 +1,71 @@
+/**
+ * 809. Expressive Words
+ * https://leetcode.com/problems/expressive-words/
+ * Difficulty: Medium
+ *
+ * Sometimes people repeat letters to represent extra feeling. For example:
+ * - "hello" -> "heeellooo"
+ * - "hi" -> "hiiii"
+ *
+ * In these strings like "heeellooo", we have groups of adjacent letters that are all the
+ * same: "h", "eee", "ll", "ooo".
+ *
+ * You are given a string s and an array of query strings words. A query word is stretchy
+ * if it can be made to be equal to s by any number of applications of the following extension
+ * operation: choose a group consisting of characters c, and add some number of characters
+ * c to the group so that the size of the group is three or more.
+ *
+ * For example, starting with "hello", we could do an extension on the group "o" to get
+ * "hellooo", but we cannot get "helloo" since the group "oo" has a size less than three.
+ * Also, we could do another extension like "ll" -> "lllll" to get "helllllooo". If
+ * s = "helllllooo", then the query word "hello" would be stretchy because of these two
+ * extension operations: query = "hello" -> "hellooo" -> "helllllooo" = s.
+ *
+ * Return the number of query strings that are stretchy.
+ */
+
+/**
+ * @param {string} s
+ * @param {string[]} words
+ * @return {number}
+ */
+var expressiveWords = function(s, words) {
+  let result = 0;
+
+  for (const word of words) {
+    if (verify(s, word)) {
+      result++;
+    }
+  }
+
+  return result;
+};
+
+function verify(s, word) {
+  let i = 0;
+  let j = 0;
+
+  while (i < s.length && j < word.length) {
+    if (s[i] !== word[j]) return false;
+
+    const char = s[i];
+    let sCount = 0;
+
+    while (i < s.length && s[i] === char) {
+      sCount++;
+      i++;
+    }
+
+    let wordCount = 0;
+
+    while (j < word.length && word[j] === char) {
+      wordCount++;
+      j++;
+    }
+
+    if (wordCount > sCount) return false;
+    if (sCount > wordCount && sCount < 3) return false;
+  }
+
+  return i === s.length && j === word.length;
+}