Update 回溯算法去重问题的另一种写法.md

problems/回溯算法去重问题的另一种写法.md

@@ -525,10 +525,41 @@ function permuteUnique(nums: number[]): number[][] {
 };
 ```
 
-Go：
+Rust：
 
+**90.子集II**：
 
+```rust
+use std::collections::HashSet;
+impl Solution {
+    pub fn subsets_with_dup(mut nums: Vec<i32>) -> Vec<Vec<i32>> {
+        let mut res = vec![];
+        let mut path = vec![];
+        nums.sort();
+        Self::backtracking(&nums, &mut path, &mut res, 0);
+        res
+    }
 
+    pub fn backtracking(
+        nums: &Vec<i32>,
+        path: &mut Vec<i32>,
+        res: &mut Vec<Vec<i32>>,
+        start_index: usize,
+    ) {
+        res.push(path.clone());
+        let mut helper_set = HashSet::new();
+        for i in start_index..nums.len() {
+            if helper_set.contains(&nums[i]) {
+                continue;
+            }
+            helper_set.insert(nums[i]);
+            path.push(nums[i]);
+            Self::backtracking(nums, path, res, i + 1);
+            path.pop();
+        }
+    }
+}
+```
 
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