feat: add swift implementation to lcof2 problem: No.076 (#3410)

Author: klever34

lcof2/剑指 Offer II 076. 数组中的第 k 大的数字/README.md

@@ -180,6 +180,41 @@ func quickSort(nums []int, left, right, k int) int {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func findKthLargest(_ nums: [Int], _ k: Int) -> Int {
+        var nums = nums
+        let n = nums.count
+        return quickSelect(&nums, 0, n - 1, n - k)
+    }
+
+    private func quickSelect(_ nums: inout [Int], _ left: Int, _ right: Int, _ k: Int) -> Int {
+        if left == right {
+            return nums[left]
+        }
+
+        var i = left - 1
+        var j = right + 1
+        let pivot = nums[(left + right) / 2]
+
+        while i < j {
+            repeat { i += 1 } while nums[i] < pivot
+            repeat { j -= 1 } while nums[j] > pivot
+            if i < j {
+                nums.swapAt(i, j)
+            }
+        }
+
+        if j < k {
+            return quickSelect(&nums, j + 1, right, k)
+        }
+        return quickSelect(&nums, left, j, k)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 076. 数组中的第 k 大的数字/Solution.swift

@@ -0,0 +1,30 @@
+class Solution {
+    func findKthLargest(_ nums: [Int], _ k: Int) -> Int {
+        var nums = nums
+        let n = nums.count
+        return quickSelect(&nums, 0, n - 1, n - k)
+    }
+
+    private func quickSelect(_ nums: inout [Int], _ left: Int, _ right: Int, _ k: Int) -> Int {
+        if left == right {
+            return nums[left]
+        }
+        
+        var i = left - 1
+        var j = right + 1
+        let pivot = nums[(left + right) / 2]
+        
+        while i < j {
+            repeat { i += 1 } while nums[i] < pivot
+            repeat { j -= 1 } while nums[j] > pivot
+            if i < j {
+                nums.swapAt(i, j)
+            }
+        }
+        
+        if j < k {
+            return quickSelect(&nums, j + 1, right, k)
+        }
+        return quickSelect(&nums, left, j, k)
+    }
+}