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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.
开始理解题意错误，每次读入4个字符，不是从buf里读入的，而是从文件里读入的，存入buf. 如果read4 < 4, 则说明已读到文件结尾。同时想到file.length > n, 则每次要确定读入Buf的正确长度，即Max.min(count, n - total)
Java code:
/* The read4 API is defined in the parent class Reader4. int read4(char[] buf); */ 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) { boolean eof = false; //end of file char[] temp = new char[4]; int total = 0; while(!eof && total < n){ int count = read4(temp); if(count < 4){ eof = true; } // get the actual count count = Math.min(count, n - total); for(int i = 0; i< count; i++){ buf[total++] = temp[i]; } } return total; } }
Reference:
1. https://leetcode.com/discuss/44743/another-accepted-java-solution
2. http://bangbingsyb.blogspot.com/2014/11/leetcode-read-n-characters-given-read4.html
Leetcode Read N Characters Given Read4
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原文地址：http://www.cnblogs.com/anne-vista/p/4865612.html
