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

@@ -604,6 +604,44 @@ impl Solution {
 }
 ```
 
+**47. 全排列 II**
+
+```rust
+use std::collections::HashSet;
+impl Solution {
+    pub fn permute_unique(mut nums: Vec<i32>) -> Vec<Vec<i32>> {
+        let mut res = vec![];
+        let mut path = vec![];
+        let mut used = vec![false; nums.len()];
+        Self::backtracking(&mut res, &mut path, &nums, &mut used);
+        res
+    }
+    pub fn backtracking(
+        res: &mut Vec<Vec<i32>>,
+        path: &mut Vec<i32>,
+        nums: &Vec<i32>,
+        used: &mut Vec<bool>,
+    ) {
+        if path.len() == nums.len() {
+            res.push(path.clone());
+            return;
+        }
+        let mut helper_set = HashSet::new();
+        for i in 0..nums.len() {
+            if used[i] || helper_set.contains(&nums[i]) {
+                continue;
+            }
+            helper_set.insert(nums[i]);
+            path.push(nums[i]);
+            used[i] = true;
+            Self::backtracking(res, path, nums, used);
+            used[i] = false;
+            path.pop();
+        }
+    }
+}
+```
+
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