feat: add swift implementation to lcof2 problem: No.009 (#2979)

Author: klever34

lcof2/剑指 Offer II 009. 乘积小于 K 的子数组/README.md

@@ -149,6 +149,31 @@ function numSubarrayProductLessThanK(nums: number[], k: number): number {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func numSubarrayProductLessThanK(_ nums: [Int], _ k: Int) -> Int {
+        if k <= 1 { return 0 }
+        
+        var product: Int = 1
+        var ans: Int = 0
+        var left: Int = 0
+        
+        for right in 0..<nums.count {
+            product *= nums[right]
+            while product >= k {
+                product /= nums[left]
+                left += 1
+            }
+            ans += right - left + 1
+        }
+        
+        return ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 009. 乘积小于 K 的子数组/Solution.swift

@@ -0,0 +1,20 @@
+class Solution {
+    func numSubarrayProductLessThanK(_ nums: [Int], _ k: Int) -> Int {
+        if k <= 1 { return 0 }
+        
+        var product: Int = 1
+        var ans: Int = 0
+        var left: Int = 0
+        
+        for right in 0..<nums.count {
+            product *= nums[right]
+            while product >= k {
+                product /= nums[left]
+                left += 1
+            }
+            ans += right - left + 1
+        }
+        
+        return ans
+    }
+}