feat: add swift implementation to lcof2 problem: No.084 (#3469)

Author: klever34

lcof2/剑指 Offer II 084. 含有重复元素集合的全排列/README.md

@@ -222,6 +222,40 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func permuteUnique(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var path = [Int]()
+        var used = [Bool](repeating: false, count: nums.count)
+        let sortedNums = nums.sorted()
+        dfs(0, sortedNums.count, sortedNums, &used, &path, &res)
+        return res
+    }
+
+    private func dfs(
+        _ u: Int, _ n: Int, _ nums: [Int], _ used: inout [Bool], _ path: inout [Int], _ res: inout [[Int]]
+    ) {
+        if u == n {
+            res.append(path)
+            return
+        }
+        for i in 0..<n {
+            if used[i] || (i > 0 && nums[i] == nums[i - 1] && !used[i - 1]) {
+                continue
+            }
+            path.append(nums[i])
+            used[i] = true
+            dfs(u + 1, n, nums, &used, &path, &res)
+            used[i] = false
+            path.removeLast()
+        }
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 084. 含有重复元素集合的全排列/Solution.swift

@@ -0,0 +1,29 @@
+class Solution {
+    func permuteUnique(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var path = [Int]()
+        var used = [Bool](repeating: false, count: nums.count)
+        let sortedNums = nums.sorted()
+        dfs(0, sortedNums.count, sortedNums, &used, &path, &res)
+        return res
+    }
+
+    private func dfs(
+        _ u: Int, _ n: Int, _ nums: [Int], _ used: inout [Bool], _ path: inout [Int], _ res: inout [[Int]]
+    ) {
+        if u == n {
+            res.append(path)
+            return
+        }
+        for i in 0..<n {
+            if used[i] || (i > 0 && nums[i] == nums[i - 1] && !used[i - 1]) {
+                continue
+            }
+            path.append(nums[i])
+            used[i] = true
+            dfs(u + 1, n, nums, &used, &path, &res)
+            used[i] = false
+            path.removeLast()
+        }
+    }
+}