leetcode 157: Read N Characters Given Read4

最新推荐文章于 2019-09-06 20:22:39 发布

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最新推荐文章于 2019-09-06 20:22:39 发布

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本文介绍了一种利用read4 API实现readN的方法，通过继承Reader4类并重写read方法，可以实现在给定缓冲区中读取指定数量字符的功能。此方法适用于文件读取场景，特别当文件大小未知或需要按需读取时。

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Read N Characters Given Read4

Total Accepted: 960 Total Submissions: 3775

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 readsn characters from the file.

Note:
The read function will only be called once for each test case.

[分析]

None

[注意]

None

[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) {
        if(buf==null || n<=0) return 0;
        int i=0;
        char[] temp = new char[4];
        while(n>0) {
            int x = read4(temp);
            int j = 0;
            int k = x;
            while(n>0 && x>0) {
                buf[i++] = temp[j++];
                --x;
                --n;
            }
            if(k<4) break;
        }
        return i;
    }
 }