a

Author: anishLearnsToCode

src/SubsetsII.java

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+import java.util.ArrayList;
+import java.util.HashMap;
+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);
+        final List<List<Integer>> result = new ArrayList<>();
+        computeSubSets(frequencies, result, new LinkedList<>(), 0, nums.length);
+        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);
+        }
+        return frequencies;
+    }
+}