feat: add swift implementation to lcof2 problem: No.119 (doocs#3712)

Author: klever34

lcof2/剑指 Offer II 119. 最长连续序列/README.md

@@ -221,6 +221,34 @@ var longestConsecutive = function (nums) {
 };
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func longestConsecutive(_ nums: [Int]) -> Int {
+        let n = nums.count
+        if n < 2 {
+            return n
+        }
+        
+        let sortedNums = Array(Set(nums)).sorted()
+        var ans = 1
+        var currentStreak = 1
+        
+        for i in 1..<sortedNums.count {
+            if sortedNums[i] == sortedNums[i - 1] + 1 {
+                currentStreak += 1
+                ans = max(ans, currentStreak)
+            } else {
+                currentStreak = 1
+            }
+        }
+        
+        return ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 119. 最长连续序列/Solution.swift

@@ -0,0 +1,23 @@
+class Solution {
+    func longestConsecutive(_ nums: [Int]) -> Int {
+        let n = nums.count
+        if n < 2 {
+            return n
+        }
+        
+        let sortedNums = Array(Set(nums)).sorted()
+        var ans = 1
+        var currentStreak = 1
+        
+        for i in 1..<sortedNums.count {
+            if sortedNums[i] == sortedNums[i - 1] + 1 {
+                currentStreak += 1
+                ans = max(ans, currentStreak)
+            } else {
+                currentStreak = 1
+            }
+        }
+        
+        return ans
+    }
+}