新增java用set的解法

problems/0491.递增子序列.md

@@ -203,6 +203,30 @@ public:
 
 
 ### Java 
+```Java
+//using set, aligned with the unimproved method
+class Solution {
+    List<List<Integer>> result = new ArrayList<>();
+    List<Integer> path = new ArrayList<>();
+    public List<List<Integer>> findSubsequences(int[] nums) {
+        backTracking(nums, 0);
+        return result;
+    }
+    private void backTracking(int[] nums, int startIndex){
+        if(path.size() >= 2)
+                result.add(new ArrayList<>(path));            
+        HashSet<Integer> hs = new HashSet<>();
+        for(int i = startIndex; i < nums.length; i++){
+            if(!path.isEmpty() && path.get(path.size() -1 ) > nums[i] || hs.contains(nums[i]))
+                continue;
+            hs.add(nums[i]);
+            path.add(nums[i]);
+            backTracking(nums, i + 1);
+            path.remove(path.size() - 1);
+        }
+    }
+}
+```
 
 ```java
 class Solution {