LeetCode491

递增子序列
考察知识点：DFS+Set(去重)
样例：
[4, 6, 7, 7]
ans:
[4,6] [4,7] [4,6,7] [4,7,7] [4,6,7,7]
[6,7] [6,7,7]
[7,7]

public static List<List<Integer>> findSubsequences(int[] nums){
     
        Set<List<Integer>> paths = new HashSet<>();  //HashSet去重
        List<Integer> path = new LinkedList<>();
        dfs(nums,0,paths,path);
        return new LinkedList<>(paths);  //Set>转List>
}

public static void dfs(int[] nums,int pos,Set<List<Integer>> paths,List<Integer> path){
     
   if(path.size()>=2){
     
       paths.add(new LinkedList<>(path));   //path为引用地址，需new LinkedList实例化添加，不然结果集paths为空
   }
   for(int i=pos;i<nums.length;i++){
     
       if(path.size()==0 || path.get(path.size()-1)<=nums[i]){
     
           path.add(nums[i]);
           dfs(nums,i+1,paths,path);
           path.remove(path.size()-1);
       }
   }
}