feat: add swift implementation to lcof2 problem: No.072 (#3305)

Author: klever34

lcof2/剑指 Offer II 072. 求平方根/README.md

@@ -160,6 +160,29 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func mySqrt(_ x: Int) -> Int {
+        if x == 0 {
+            return 0
+        }
+        var left = 0
+        var right = x
+        while left < right {
+            let mid = (left + right + 1) / 2
+            if mid <= x / mid {
+                left = mid
+            } else {
+                right = mid - 1
+            }
+        }
+        return left
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 072. 求平方根/Solution.swift

@@ -0,0 +1,18 @@
+class Solution {
+    func mySqrt(_ x: Int) -> Int {
+        if x == 0 {
+            return 0
+        }
+        var left = 0
+        var right = x
+        while left < right {
+            let mid = (left + right + 1) / 2
+            if mid <= x / mid {
+                left = mid
+            } else {
+                right = mid - 1
+            }
+        }
+        return left
+    }
+}