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| 1 | +import java.util.ArrayList; |
| 2 | +import java.util.HashMap; |
| 3 | +import java.util.LinkedList; |
| 4 | +import java.util.List; |
| 5 | +import java.util.Map; |
| 6 | + |
| 7 | +public class SubsetsII { |
| 8 | + public List<List<Integer>> subsetsWithDup(int[] nums) { |
| 9 | + final Map<Integer, Integer> frequencies = getElementFrequencies(nums); |
| 10 | + final List<List<Integer>> result = new ArrayList<>(); |
| 11 | + computeSubSets(frequencies, result, new LinkedList<>(), 0, nums.length); |
| 12 | + return result; |
| 13 | + } |
| 14 | + |
| 15 | + private void computeSubSets(Map<Integer, Integer> frequencies, List<List<Integer>> result, LinkedList<Integer> current, int depth, int maxDepth) { |
| 16 | + if (depth == maxDepth) { |
| 17 | + result.add(new ArrayList<>(current)); |
| 18 | + return; |
| 19 | + } |
| 20 | + for (Map.Entry<Integer, Integer> entry : frequencies.entrySet()) { |
| 21 | + if (entry.getValue() > 0) { |
| 22 | + entry.setValue(entry.getValue() - 1); |
| 23 | + computeSubSets(frequencies, result, current, depth + 1, maxDepth); |
| 24 | + current.add(entry.getKey()); |
| 25 | + computeSubSets(frequencies, result, current, depth + 1, maxDepth); |
| 26 | + current.removeLast(); |
| 27 | + entry.setValue(entry.getValue() + 1); |
| 28 | + } |
| 29 | + } |
| 30 | + } |
| 31 | + |
| 32 | + private Map<Integer, Integer> getElementFrequencies(int[] array) { |
| 33 | + final Map<Integer, Integer> frequencies = new HashMap<>(); |
| 34 | + for (int element : array) { |
| 35 | + frequencies.put(element, frequencies.getOrDefault(element, 0) + 1); |
| 36 | + } |
| 37 | + return frequencies; |
| 38 | + } |
| 39 | +} |
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