LintCode-17. 子集

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

public class Solution {
    
    /*
     * @param nums: A set of numbers
     * @return: A list of lists
     */
    public List<List<Integer>> subsets(int[] nums) {
        // write your code here
        List<List<Integer>>  aList = new ArrayList<List<Integer>>();
        aList.add(new ArrayList<Integer>());
        for (int num : nums){
            int size =  aList.size();
            for(int i =  0; i < size; i++){
                List<Integer> temp = new ArrayList<>(aList.get(i));
                temp.add(num);
                Collections.sort(temp);
                aList.add(temp);
            }
        }
        return aList;
    }
}