Given a collection of integers that might contain duplicates, nums, return all possible subsets.
Note: The solution set must not contain duplicate subsets.
For example,
If nums = [1,2,2], a solution is:
[ [2], [1], [1,2,2], [2,2], [1,2], [] ]
public class Solution {
public List<List<Integer>> subsetsWithDup(int[] nums) {
List<List<Integer>> result = new ArrayList<List<Integer>>();
if(nums == null || nums.length == 0) {
return result;
}
List<Integer> list = new ArrayList<Integer>();
Arrays.sort(nums);
backtrack(result, list, nums, 0);
return result;
}
public void backtrack(List<List<Integer>> result, List<Integer> list, int[] nums, int position) {
if(list.size() > nums.length) {
return;
}
result.add(new ArrayList<Integer>(list));
for(int i = position; i < nums.length; i++) {
if(i > position && nums[i] == nums[i - 1]) {
continue;
}
list.add(nums[i]);
backtrack(result, list, nums, i + 1);
list.remove(list.size() - 1);
}
}
}
原文：http://www.cnblogs.com/superzhaochao/p/6387752.html