From 043a6f974987bca40c5babf37646c4e0ac574908 Mon Sep 17 00:00:00 2001
From: Yi Gu <rio.deliberate@gmail.com>
Date: Wed, 21 Mar 2018 21:24:40 -0700
Subject: [PATCH] [Stack] Optimize solution to Valid Parentheses

---
 Stack/ValidParentheses.swift | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Stack/ValidParentheses.swift b/Stack/ValidParentheses.swift
index 7a42a7fd..302ee9f2 100644
--- a/Stack/ValidParentheses.swift
+++ b/Stack/ValidParentheses.swift
@@ -5,10 +5,10 @@
  */
 
 class ValidParentheses {
-    func isValid(s: String) -> Bool {
+    func isValid(_ s: String) -> Bool {
         var stack = [Character]()
         
-        for char in s.characters {
+        for char in s {
             if char == "(" || char == "[" || char == "{" {
                 stack.append(char)
             } else if char == ")" {
@@ -26,6 +26,6 @@ class ValidParentheses {
             }
         }
         
-        return stack.count == 0
+        return stack.isEmpty
     }
 }
\ No newline at end of file