Add solution #906

Author: JoshCrozier

Diff for: README.md

@@ -716,6 +716,7 @@
 903|[Valid Permutations for DI Sequence](./0903-valid-permutations-for-di-sequence.js)|Hard|
 904|[Fruit Into Baskets](./0904-fruit-into-baskets.js)|Medium|
 905|[Sort Array By Parity](./0905-sort-array-by-parity.js)|Easy|
+906|[Super Palindromes](./0906-super-palindromes.js)|Hard|
 909|[Snakes and Ladders](./0909-snakes-and-ladders.js)|Medium|
 912|[Sort an Array](./0912-sort-an-array.js)|Medium|
 914|[X of a Kind in a Deck of Cards](./0914-x-of-a-kind-in-a-deck-of-cards.js)|Medium|

Diff for: solutions/0906-super-palindromes.js

@@ -0,0 +1,40 @@
+/**
+ * 906. Super Palindromes
+ * https://leetcode.com/problems/super-palindromes/
+ * Difficulty: Hard
+ *
+ * Let's say a positive integer is a super-palindrome if it is a palindrome, and it is also
+ * the square of a palindrome.
+ *
+ * Given two positive integers left and right represented as strings, return the number of
+ * super-palindromes integers in the inclusive range [left, right].
+ */
+
+/**
+ * @param {string} left
+ * @param {string} right
+ * @return {number}
+ */
+var superpalindromesInRange = function(lowerBound, upperBound) {
+  let result = 9n >= lowerBound && 9n <= upperBound ? 1 : 0;
+
+  const isPalindrome = sequence => {
+    for (let start = 0, end = sequence.length - 1; start < end; start++, end--) {
+      if (sequence[start] !== sequence[end]) return false;
+    }
+    return true;
+  };
+
+  for (let base = 1; base < 19684; base++) {
+    const ternary = base.toString(3);
+    if (isPalindrome(ternary)) {
+      const square = BigInt(ternary) * BigInt(ternary);
+      if (square > upperBound) return result;
+      if (square >= lowerBound && isPalindrome(square.toString())) {
+        result++;
+      }
+    }
+  }
+
+  return result;
+};