LeetCode，leetcodeoj

LeetCode，leetcodeoj

題目：

Given a collection of integers that might contain duplicates, nums, 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 nums = [1,2,2], a solution is:

[  [2],  [1],  [1,2,2],  [2,2],  [1,2],  []]

思路：

在subsets的代碼上加一句話if (i > start && nums[i] == nums[i - 1]) continue;

package recursion;import java.util.ArrayList;import java.util.Arrays;import java.util.List;public class SubsetsII {    public List<List<Integer>> subsetsWithDup(int[] nums) {        List<List<Integer>> res = new ArrayList<List<Integer>>();        List<Integer> record = new ArrayList<Integer>();        Arrays.sort(nums);        int n = nums.length;        for (int k = 0; k <= n; ++k)            generateRecord(res, record, nums, 0, n - 1, k);        return res;    }        private void generateRecord(List<List<Integer>> res, List<Integer> record, int[] nums, int start, int end, int k) {        if (k == 0) {            res.add(record);            return;        }                for (int i = start; i <= end - k + 1; ++i) {             if (i > start && nums[i] == nums[i - 1]) continue;            List<Integer> newRecord = new ArrayList<Integer>(record);            newRecord.add(nums[i]);            generateRecord(res, newRecord, nums, i + 1, end, k - 1);        }    }        public static void main(String[] args) {        // TODO Auto-generated method stub        SubsetsII s = new SubsetsII();        int[] nums = { 1, 2, 2, 3 };        List<List<Integer>> res = s.subsetsWithDup(nums);        for (List<Integer> l : res) {            for (int i : l)                 System.out.print(i + "\t");            System.out.println();        }    }}