添加 0090.子集II.md Scala版本

problems/0090.子集II.md

@@ -434,6 +434,63 @@ func subsetsWithDup(_ nums: [Int]) -> [[Int]] {
 }
 ```
 
+### Scala
+
+不使用userd数组:
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def subsetsWithDup(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.ListBuffer[List[Int]]()
+    var path = mutable.ListBuffer[Int]()
+    var num = nums.sorted // 排序
+
+    def backtracking(startIndex: Int): Unit = {
+      result.append(path.toList)
+      if (startIndex >= num.size){
+        return
+      }
+      for (i <- startIndex until num.size) {
+        // 同一树层重复的元素不进入回溯
+        if (!(i > startIndex && num(i) == num(i - 1))) {
+          path.append(num(i))
+          backtracking(i + 1)
+          path.remove(path.size - 1)
+        }
+      }
+    }
+
+    backtracking(0)
+    result.toList
+  }
+}
+```
+
+使用Set去重:
+```scala
+object Solution {
+  import scala.collection.mutable
+  def subsetsWithDup(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.Set[List[Int]]()
+    var num = nums.sorted
+    def backtracking(path: mutable.ListBuffer[Int], startIndex: Int): Unit = {
+      if (startIndex == num.length) {
+        result.add(path.toList)
+        return
+      }
+      path.append(num(startIndex))
+      backtracking(path, startIndex + 1)  // 选择
+      path.remove(path.size - 1)
+      backtracking(path, startIndex + 1)  // 不选择
+    }
+
+    backtracking(mutable.ListBuffer[Int](), 0)
+
+    result.toList
+  }
+}
+```
 
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