Add solution #1291

Author: JoshCrozier

solutions/1291-sequential-digits.js

@@ -0,0 +1,29 @@
+/**
+ * 1291. Sequential Digits
+ * https://leetcode.com/problems/sequential-digits/
+ * Difficulty: Medium
+ *
+ * An integer has sequential digits if and only if each digit in the number is one more than the previous digit.
+ * Return a sorted list of all the integers in the range [low, high] inclusive that have sequential digits.
+ */
+
+/**
+ * @param {number} low
+ * @param {number} high
+ * @return {number[]}
+ */
+var sequentialDigits = function(low, high) {
+  return getSequentialNumbers().filter(n => n >= low && n <= high);
+};
+
+function getSequentialNumbers() {
+  const numbers = new Set([]);
+
+  for (let i = 0; i < 10; i++) {
+    for (let j = 9; j > 0 && j > i + 1; j--) {
+      numbers.add(+'123456789'.slice(i, j));
+    }
+  }
+
+  return [...numbers].sort((a, b) => a - b);
+}