solves subsets II

Author: anishLearnsToCode

README.md

@@ -80,6 +80,7 @@
 |  86  | [Partition List](https://leetcode.com/problems/partition-list)                                                                                            |                                                                  [![Java](assets/java.png)](src/PartitionList.java)                                                                  |                                                                                                                                   |
 |  88  | [Merge Sorted Array](https://leetcode.com/problems/merge-sorted-array)                                                                                    |                                  [![Java](assets/java.png)](src/MergeSortedArray.java) [![Python](assets/python.png)](python/merge_sorted_array.py)                                  |                                                                                                                                   |
 |  89  | [Gray Code](https://leetcode.com/problems/gray-code)                                                                                                      |                                                                    [![Java](assets/java.png)](src/GrayCode.java)                                                                     |                                                                                                                                   |
+|  90  | [Subsets II](https://leetcode.com/problems/subsets-ii)                                                                                                    |                                                                    [![Java](assets/java.png)](src/SubsetsII.java)                                                                    |                                                                                                                                   |
 |  94  | [Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/)                                                             |                       [![Java](assets/java.png)](src/BinaryTreeInorderTraversal.java) [![Python](assets/python.png)](python/binary_tree_inorder_traversal.py)                        |                                                                                                                                   |
 | 100  | [Same Tree](https://leetcode.com/problems/same-tree)                                                                                                      |                                          [![Java](assets/java.png)](src/SameTree.java) [![Python](assets/python.png)](python/same_tree.py)                                           |                                                                                                                                   |
 | 101  | [Symmetric Tree](https://leetcode.com/problems/symmetric-tree)                                                                                            |                                     [![Java](assets/java.png)](src/SymmetricTree.java) [![Python](assets/python.png)](python/symmetric_tree.py)                                      |                                                                                                                                   |

src/SubsetsII.java

@@ -1,39 +1,27 @@
+// https://leetcode.com/problems/subsets-ii
+// T: O(2^n)
+// S: O(n * 2^n)
+
 import java.util.ArrayList;
-import java.util.HashMap;
+import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
-import java.util.Map;
 
 public class SubsetsII {
     public List<List<Integer>> subsetsWithDup(int[] nums) {
-        final Map<Integer, Integer> frequencies = getElementFrequencies(nums);
+        Arrays.sort(nums);
         final List<List<Integer>> result = new ArrayList<>();
-        computeSubSets(frequencies, result, new LinkedList<>(), 0, nums.length);
+        helper(result, new LinkedList<>(), nums, 0);
         return result;
     }
 
-    private void computeSubSets(Map<Integer, Integer> frequencies, List<List<Integer>> result, LinkedList<Integer> current, int depth, int maxDepth) {
-        if (depth == maxDepth) {
-            result.add(new ArrayList<>(current));
-            return;
-        }
-        for (Map.Entry<Integer, Integer> entry : frequencies.entrySet()) {
-            if (entry.getValue() > 0) {
-                entry.setValue(entry.getValue() - 1);
-                computeSubSets(frequencies, result, current, depth + 1, maxDepth);
-                current.add(entry.getKey());
-                computeSubSets(frequencies, result, current, depth + 1, maxDepth);
-                current.removeLast();
-                entry.setValue(entry.getValue() + 1);
-            }
-        }
-    }
-
-    private Map<Integer, Integer> getElementFrequencies(int[] array) {
-        final Map<Integer, Integer> frequencies = new HashMap<>();
-        for (int element : array) {
-            frequencies.put(element, frequencies.getOrDefault(element, 0) + 1);
+    public void helper(List<List<Integer>> result, LinkedList<Integer> current, int[] numbers, int index) {
+        result.add(new ArrayList<>(current));
+        for(int i = index ; i < numbers.length ; i++) {
+            if(i > index && numbers[i] == numbers[i-1]) continue;
+            current.add(numbers[i]);
+            helper(result, current, numbers, i + 1);
+            current.removeLast();
         }
-        return frequencies;
     }
 }