Add solution #357

Author: JoshCrozier

README.md

@@ -285,6 +285,7 @@
 352|[Data Stream as Disjoint Intervals](./0352-data-stream-as-disjoint-intervals.js)|Hard|
 354|[Russian Doll Envelopes](./0354-russian-doll-envelopes.js)|Hard|
 355|[Design Twitter](./0355-design-twitter.js)|Medium|
+357|[Count Numbers with Unique Digits](./0357-count-numbers-with-unique-digits.js)|Medium|
 367|[Valid Perfect Square](./0367-valid-perfect-square.js)|Easy|
 371|[Sum of Two Integers](./0371-sum-of-two-integers.js)|Medium|
 372|[Super Pow](./0372-super-pow.js)|Medium|

solutions/0357-count-numbers-with-unique-digits.js

@@ -0,0 +1,21 @@
+/**
+ * 357. Count Numbers with Unique Digits
+ * https://leetcode.com/problems/count-numbers-with-unique-digits/
+ * Difficulty: Medium
+ *
+ * Given an integer n, return the count of all numbers with unique digits, x, where 0 <= x < 10n.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var countNumbersWithUniqueDigits = function(n) {
+  if (n === 0) return 1;
+  if (n > 10) return countNumbersWithUniqueDigits(10);
+  let result = 9;
+  for (let i = 0; i < n - 1; i++) {
+    result *= (9 - i);
+  }
+  return result + countNumbersWithUniqueDigits(n - 1);
+};