子集问题

78.子集，90集合II(数组中含有重复元素)，491递增子序列
78.子集

private List<List<Integer>>res=new ArrayList<>();
    private List<Integer>singleRes=new LinkedList<>();
    public List<List<Integer>> subsets(int[] nums) {
        res.add(new ArrayList<>());
        backTrack(0,nums);
        return res;
    }
    private void backTrack(int index,int[] nums){
        if(singleRes.size()>0) {
            res.add(new ArrayList<>(singleRes));
        }
        if(index>=nums.length){
            return;
        }
        for(int i=index;i<nums.length;i++){
            singleRes.add(nums[i]);
            backTrack(i+1,nums);
            singleRes.remove(singleRes.size()-1);
        }
    }

90.子集2

private List<List<Integer>>res=new ArrayList<>();
private List<Integer>singleRes=new LinkedList<>();
public List<List<Integer>> subsetsWithDup(int[] nums) {
  res.add(new ArrayList<>());
  Arrays.sort(nums);
  backTrack(0,nums);
  return res;
}
private void backTrack(int index,int[]nums){
  if(singleRes.size()>0){
    res.add(new ArrayList<>(singleRes));
  }
  if(index>=nums.length){
    return;
  }
  for(int i=index;i<nums.length;i++){
    if(i>index&&nums[i]==nums[i-1]){
      continue;
    }
    singleRes.add(nums[i]);
    backTrack(i+1,nums);
    singleRes.remove(singleRes.size()-1);
  }
}

491.递增子序列

private List<List<Integer>>res=new ArrayList<>();
private List<Integer>singleRes=new LinkedList<>();
public List<List<Integer>> findSubsequences(int[] nums) {
  backTrack(0,nums,Integer.MIN_VALUE);
  return res;
}
private void backTrack(int index,int[]nums,int lastNum){
  if(singleRes.size()>=2){
    res.add(new ArrayList<>(singleRes));
  }
  if(index>=nums.length){
    return;
  }
  boolean[] vis = new boolean[201];
  for(int i=index;i<nums.length;i++){
    if(nums[i]<lastNum){
      continue;
    }
    if(vis[nums[i]+100]){
      continue;
    }
    singleRes.add(nums[i]);
    vis[nums[i]+100]=true;
    backTrack(i+1,nums,nums[i]);
    singleRes.remove(singleRes.size()-1);
  }
}