157. Read N Characters Given Read4

题目：

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.

链接： http://leetcode.com/problems/read-n-characters-given-read4/

2/19/2017, Java，答案抄的

思路，每次尝试读4个到临时temp buffer中，然后按照n来赋值到buf。

不要直接read4读到buf中

public class Solution extends Reader4 {
    /**
     * @param buf Destination buffer
     * @param n   Maximum number of characters to read
     * @return    The number of characters read
     */
    public int read(char[] buf, int n) {
        char[] temp = new char[4];
        int totalSize = 0;
        int size = 0;
        
        while((size = read4(temp)) > 0) {
            for (int i = 0; i < size && totalSize < n; i++) {
                buf[totalSize++] = temp[i];
            }
            if (totalSize >= n) break;
        }
        return totalSize;
    }
}