[Swift]LeetCode157.用Read4來讀取N個字符 $ Read N Characters Given Read4

★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★
➤微信公衆號：山青詠芝（shanqingyongzhi）
➤博客園地址：山青詠芝（https://www.cnblogs.com/strengthen/）
➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：http://www.javashuo.com/article/p-rfnfsjqy-me.html 
➤若是連接不是山青詠芝的博客園地址，則多是爬取做者的文章。
➤原文已修改更新！強烈建議點擊原文地址閱讀！支持做者！支持原創！
★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★

The API: int read4(char *buf) reads 4 characters at a time from a file.
The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the file.
By using the read4 API, implement the function int read(char *buf, int n) that reads n characters from the file.
Note:
The read function will only be called once for each test case.

---

API：int Read 4（char *BUF）每次從一個文件讀取4個字符。

返回值是讀取的實際字符數。例如，若是文件中只剩下3個字符，則返回3。

經過使用read4 API，實現從文件中讀取n個字符的int read（char*buf，int n）函數。

注：

讀取函數只對每一個測試用例調用一次。

---

 1 class Solution {
 2     func read(_ buf:[Character],_ n:Int) -> Int {
 3         var res:Int = 0
 4         for i in 0...n
 5         {
 6             var cur:Int = read4(buf + res)
 7             if cur == 0 {break}
 8             res += cur
 9         }
10         return min(res, n)
11     }
12 }