// Source : https://oj.leetcode.com/problems/subsets-ii/ // Inspired by : http://www.jiuzhang.com/solutions/subsets-ii/ // Author : Lei Cao // Date : 2015-10-02 /********************************************************************************** * * Given a collection of integers that might contain duplicates, S, return all possible subsets. * * Note: * * Elements in a subset must be in non-descending order. * The solution set must not contain duplicate subsets. * * For example, * If S = [1,2,2], a solution is: * * [ * [2], * [1], * [1,2,2], * [2,2], * [1,2], * [] * ] * * **********************************************************************************/ package subsets; import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.List; public class subsetsII { /** * Leetcode version * @param nums * @return */ public List> subsetsWithDup(int [] nums) { List> result = new ArrayList>(); if (nums == null || nums.length == 0) { return result; } ArrayList list = new ArrayList(); Arrays.sort(nums); addSubset(result, list, nums, 0); return result; } private void addSubset(List> result, ArrayList list, int[] nums, int pos) { result.add(new ArrayList(list)); for (int i = pos; i < nums.length; i++) { // in this level, if current loop is not the start element, check if it's duplicated with the previous element if (i != pos && nums[i - 1] == nums[i]) { continue; } list.add(nums[i]); addSubset(result, list, nums, i + 1); list.remove(list.size() - 1); } } /** * Lintcode version * @param S: A set of numbers. * @return: A list of lists. All valid subsets. */ public ArrayList> subsetsWithDup(ArrayList s) { // write your code here ArrayList> result = new ArrayList>(); if (s == null || s.size() == 0) { return result; } ArrayList list = new ArrayList(); Collections.sort(s); addSubset(s, result, list, 0); return result; } private void addSubset( ArrayList s, ArrayList> result, ArrayList list, int pos) { result.add(new ArrayList(list)); for (int i = pos; i < s.size(); i++) { if (i != pos && s.get(i - 1) == s.get(i)) { continue; } list.add(s.get(i)); addSubset(s, result, list, i + 1); list.remove(list.size() - 1); } } }