🎉 feat: initial commit for leetcode 394 using Swift

Author: liuchuo

Swift/394. Decode String.swift

@@ -0,0 +1,23 @@
+// 394. Decode String
+// 12 ms, 35.71%
+func decodeString(_ s: String) -> String {
+    var stack = [String]()
+    s.forEach {
+        switch $0 {
+        case "]":
+            var s = "", i = ""
+            while let c = stack.popLast(), c != "[" {
+                s = "\(c)\(s)"
+            }
+            while let sl = stack.last, nil != Int("\(sl)"), let c = stack.popLast() {
+                i = "\(c)\(i)"
+            }
+            stack.append(String(repeating: s, count: Int(i)!))
+        default:
+            stack.append(String($0))
+        }
+    }
+
+    return stack.joined()
+}
+