Add solution #47

Author: JoshCrozier

README.md

@@ -49,6 +49,7 @@
 42|[Trapping Rain Water](./0042-trapping-rain-water.js)|Hard|
 43|[Multiply Strings](./0043-multiply-strings.js)|Medium|
 46|[Permutations](./0046-permutations.js)|Medium|
+47|[Permutations II](./0047-permutations-ii.js)|Medium|
 48|[Rotate Image](./0048-rotate-image.js)|Medium|
 49|[Group Anagrams](./0049-group-anagrams.js)|Medium|
 50|[Pow(x, n)](./0050-powx-n.js)|Medium|

solutions/0047-permutations-ii.js

@@ -0,0 +1,32 @@
+/**
+ * 47. Permutations II
+ * https://leetcode.com/problems/permutations-ii/
+ * Difficulty: Medium
+ *
+ * Given a collection of numbers, nums, that might contain duplicates,
+ * return all possible unique permutations in any order.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+var permuteUnique = function(nums) {
+  const result = new Set();
+  backtrack(result, nums);
+  return Array.from(result).map(s => s.split(','));
+};
+
+function backtrack(result, nums, order = []) {
+  if (!nums.length) {
+    result.add(order.join());
+  } else {
+    for (let i = 0; i < nums.length; i++) {
+      backtrack(
+        result,
+        [...nums.slice(0, i), ...nums.slice(i + 1)],
+        [...order, nums[i]],
+      );
+    }
+  }
+}