Add subsets II LC medium JS solution

Author: nwthomas

src/leetcode/medium/medium.md

@@ -70,6 +70,7 @@
 -   [Sort Colors](#sort-colors)
 -   [Spiral Matrix](spiral-matrix)
 -   [Subsets](subsets)
+-   [Subsets II](subsets-ii)
 -   [Target Sum](target-sum)
 -   [Time-Based Key Value Store](time-based-key-value-store)
 -   [Top K Frequent ELements](top-k-frequent-elements)

src/leetcode/medium/subsets-ii/subsetsII.js

@@ -0,0 +1,46 @@
+/*
+https://leetcode.com/problems/subsets-ii/description
+
+Given an integer array nums that may contain duplicates, return all possible subsets (the power set).
+
+The solution set must not contain duplicate subsets. Return the solution in any order.
+
+Example 1:
+Input: nums = [1,2,2]
+Output: [[],[1],[1,2],[1,2,2],[2],[2,2]]
+
+Example 2:
+Input: nums = [0]
+Output: [[],[0]]
+ 
+Constraints:
+1 <= nums.length <= 10
+-10 <= nums[i] <= 10
+*/
+
+const subsetsWithDup = (nums) => {
+    nums.sort((a, b) => a - b);
+
+    function backtrack(step = 0, subset = []) {
+        if (step >= nums.length) {
+            return [subset];
+        }
+
+        const result = [subset];
+        let prev = -Infinity;
+        for (let i = step; i < nums.length; i++) {
+            const currentNum = nums[i];
+
+            if (currentNum !== prev) {
+                prev = currentNum;
+                result.push(...backtrack(i + 1, [...subset, currentNum]));
+            }
+        }
+
+        return result;
+    }
+
+    return backtrack();
+};
+
+module.exports = { subsetsWithDup };

src/leetcode/medium/subsets-ii/subsetsII.test.js

@@ -0,0 +1,43 @@
+const { subsetsWithDup } = require("./subsetsII");
+
+describe("subsetsWithDup", () => {
+    it("returns all possible subsets for a short array of nums", () => {
+        const result = subsetsWithDup([1, 2, 2]);
+        expect(result).toEqual([[], [1], [1, 2], [1, 2, 2], [2], [2, 2]]);
+    });
+
+    it("returns all possible subsets for a long array of nums", () => {
+        const result = subsetsWithDup([1, 2, 2, 3, 3, 3]);
+        expect(result).toEqual([
+            [],
+            [1],
+            [1, 2],
+            [1, 2, 2],
+            [1, 2, 2, 3],
+            [1, 2, 2, 3, 3],
+            [1, 2, 2, 3, 3, 3],
+            [1, 2, 3],
+            [1, 2, 3, 3],
+            [1, 2, 3, 3, 3],
+            [1, 3],
+            [1, 3, 3],
+            [1, 3, 3, 3],
+            [2],
+            [2, 2],
+            [2, 2, 3],
+            [2, 2, 3, 3],
+            [2, 2, 3, 3, 3],
+            [2, 3],
+            [2, 3, 3],
+            [2, 3, 3, 3],
+            [3],
+            [3, 3],
+            [3, 3, 3],
+        ]);
+    });
+
+    it("returns all possible subsets for an array of same nums", () => {
+        const result = subsetsWithDup([7, 7]);
+        expect(result).toEqual([[], [7], [7, 7]]);
+    });
+});