Given a file and assume that you can only read the file using a given method
read4
, implement a method to read
n
characters.
Method read4:
The API
read4
reads 4 consecutive characters from the file, then writes those characters into the buffer array
buf
.
The return value is the number of actual characters read.
Note that
read4()
has its own file pointer, much like
FILE *fp
in C.
Definition of read4:
Parameter: char[] buf Returns: int Note: buf[] is destination not source, the results from read4 will be copied to buf[]
Below is a high level example of how
read4
works:
File file("abcdefghijk"); // File is "abcdefghijk", initially file pointer (fp) points to 'a'
char[] buf = new char[4]; // Create buffer with enough space to store characters
read4(buf); // read4 returns 4. Now buf = "abcd", fp points to 'e'
read4(buf); // read4 returns 4. Now buf = "efgh", fp points to 'i'
read4(buf); // read4 returns 3. Now buf = "ijk", fp points to end of file
Method read:
By using the
read4
method, implement the method
read
that reads
n
characters from the file and store it in the buffer array
buf
. Consider that you
cannot
manipulate the file directly.
The return value is the number of actual characters read.
Definition of read:
Parameters: char[] buf, int n Returns: int Note: buf[] is destination not source, you will need to write the results to buf[]
Example 1:
Input: file = "abc", n = 4 Output: 3 Explanation: After calling your read method, buf should contain "abc". We read a total of 3 characters from the file, so return 3. Note that "abc" is the file's content, not buf. buf is the destination buffer that you will have to write the results to.
Example 2:
Input: file = "abcde", n = 5 Output: 5 Explanation: After calling your read method, buf should contain "abcde". We read a total of 5 characters from the file, so return 5.
Example 3:
Input: file = "abcdABCD1234", n = 12 Output: 12 Explanation: After calling your read method, buf should contain "abcdABCD1234". We read a total of 12 characters from the file, so return 12.
Example 4:
Input: file = "leetcode", n = 5 Output: 5 Explanation: After calling your read method, buf should contain "leetc". We read a total of 5 characters from the file, so return 5.
Note:
read4
but
not
for
read
.
read
function will only be called once for each test case.
buf
, is guaranteed to have enough space for storing
n
characters.