Merge pull request wangzheng0822#267 from IceBlackTea/master

修复 size getter 方法导致的死循环

Author: wangzheng0822

swift/08_stack/StackBasedOnLinkedList.swift

@@ -14,8 +14,10 @@ struct StackBasedOnLinkedList<Element>: Stack {
 
  var size: Int {
  var count = 0
- while head.next != nil {
+ var cur = head.next
+ while cur != nil {
  count += 1
+ cur = cur?.next
  }
  return count
  }