feat: add swift implementation to lcof problem: No.10.1 (#2856)

Author: klever34

lcof/面试题10- I. 斐波那契数列/README.md

@@ -177,6 +177,25 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func fib(_ n: Int) -> Int {
+        var a = 0
+        var b = 1
+        var count = n
+        while count > 0 {
+            let c = (a + b) % 1000000007
+            a = b
+            b = c
+            count -= 1
+        }
+        return a
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题10- I. 斐波那契数列/Solution.swift

@@ -0,0 +1,14 @@
+class Solution {
+    func fib(_ n: Int) -> Int {
+        var a = 0
+        var b = 1
+        var count = n
+        while count > 0 {
+            let c = (a + b) % 1000000007
+            a = b
+            b = c
+            count -= 1
+        }
+        return a
+    }
+}