Add solution #187

Author: JoshCrozier

README.md

@@ -143,6 +143,7 @@
 168|[Excel Sheet Column Title](./0168-excel-sheet-column-title.js)|Easy|
 169|[Majority Element](./0169-majority-element.js)|Easy|
 179|[Largest Number](./0179-largest-number.js)|Medium|
+187|[Repeated DNA Sequences](./0187-repeated-dna-sequences.js)|Medium|
 189|[Rotate Array](./0189-rotate-array.js)|Medium|
 190|[Reverse Bits](./0190-reverse-bits.js)|Easy|
 191|[Number of 1 Bits](./0191-number-of-1-bits.js)|Easy|

solutions/0187-repeated-dna-sequences.js

@@ -0,0 +1,33 @@
+/**
+ * 187. Repeated DNA Sequences
+ * https://leetcode.com/problems/repeated-dna-sequences/
+ * Difficulty: Medium
+ *
+ * The DNA sequence is composed of a series of nucleotides abbreviated as 'A', 'C', 'G', and 'T':
+ * - For example, "ACGAATTCCG" is a DNA sequence.
+ *
+ * When studying DNA, it is useful to identify repeated sequences within the DNA.
+ *
+ * Given a string s that represents a DNA sequence, return all the 10-letter-long sequences
+ * (substrings) that occur more than once in a DNA molecule. You may return the answer in any order.
+ */
+
+/**
+ * @param {string} s
+ * @return {string[]}
+ */
+var findRepeatedDnaSequences = function(s) {
+  let substring = s.slice(0, 10);
+  const set = new Set([substring]);
+  const result = new Set();
+
+  for (let i = 10; i < s.length; i++) {
+    substring = substring.slice(1) + s[i];
+    if (set.has(substring)) {
+      result.add(substring);
+    }
+    set.add(substring);
+  }
+
+  return [...result];
+};