feat: add swift implementation to lcp problem: No.02 (#3719)

lcp/LCP 02. 分式化简/README.md

@@ -195,6 +195,36 @@ var fraction = function (cont) {
 };
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    private var cont: [Int] = []
+
+    func fraction(_ cont: [Int]) -> [Int] {
+        self.cont = cont
+        return dfs(0)
+    }
+
+    private func dfs(_ i: Int) -> [Int] {
+        if i == cont.count - 1 {
+            return [cont[i], 1]
+        }
+        let next = dfs(i + 1)
+        let a = next[0]
+        let b = next[1]
+        let x = a * cont[i] + b
+        let y = a
+        let g = gcd(x, y)
+        return [x / g, y / g]
+    }
+
+    private func gcd(_ a: Int, _ b: Int) -> Int {
+        return b == 0 ? a : gcd(b, a % b)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcp/LCP 02. 分式化简/Solution.swift

@@ -0,0 +1,25 @@
+class Solution {
+    private var cont: [Int] = []
+
+    func fraction(_ cont: [Int]) -> [Int] {
+        self.cont = cont
+        return dfs(0)
+    }
+
+    private func dfs(_ i: Int) -> [Int] {
+        if i == cont.count - 1 {
+            return [cont[i], 1]
+        }
+        let next = dfs(i + 1)
+        let a = next[0]
+        let b = next[1]
+        let x = a * cont[i] + b
+        let y = a
+        let g = gcd(x, y)
+        return [x / g, y / g]
+    }
+
+    private func gcd(_ a: Int, _ b: Int) -> Int {
+        return b == 0 ? a : gcd(b, a % b)
+    }
+}