[Swift]LeetCode157.用Read4来读取N个字符 $ Read N Characters Given Read4

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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.

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API：int Read 4（char *BUF）每次从一个文件读取4个字符。

返回值是读取的实际字符数。例如，如果文件中只剩下3个字符，则返回3。

通过使用read4 API，实现从文件中读取n个字符的int read（char*buf，int n）函数。

注：

读取函数只对每个测试用例调用一次。

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class Solution {
    func read(_ buf:[Character],_ n:Int) -> Int {
        var res:Int = 0
        for i in 0...n
        {
            var cur:Int = read4(buf + res)
            if cur == 0 {break}
            res += cur
        }
        return min(res, n)
    }
}