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 four consecutive characters from file, then writes those characters into the buffer array buf4.
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\[\] buf4
Returns: int
buf4[] is a destination, not a source. The results from read4 will be copied to buf4[].
Below is a high-level example of how read4 works:
File file( "abcde "); // File is "abcde ", initially file pointer (fp) points to 'a' char[] buf4 = new char[4]; // Create buffer with enough space to store characters read4(buf4); // read4 returns 4. Now buf4 = "abcd ", fp points to 'e' read4(buf4); // read4 returns 1. Now buf4 = "e ", fp points to end of file read4(buf4); // read4 returns 0. Now buf4 = " ", fp points to end of file
Method read:
By using the read4 method, implement the method read that reads n characters from file and store it in the buffer array buf. Consider that you cannot manipulate file directly.
The return value is the number of actual characters read.
Definition of read:
Parameters: char\[\] buf, int n
Returns: int
buf[] is a destination, not a source. You will need to write the results to buf[].
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.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.
Constraints:
1 <= file.length <= 500file consist of English letters and digits.1 <= n <= 1000program main
implicit none
integer :: n, i, j
character(len=4) :: buf4
character(len=1000) :: file
character(len=1000), allocatable :: buf(:)
! Read n characters from file and store it in buf
call read(file, n, buf)
! Print the contents of buf
do i = 1, size(buf)
print *, buf(i)
end do
contains
subroutine read4(buf4)
implicit none
character(len=4), intent(out) :: buf4
integer :: i
! Your code here
buf4 = "abcd"
end subroutine read4
function read(file, n, buf) result(num_chars_read)
implicit none
character(len=*), intent(in) :: file
integer, intent(in) :: n
character(len=*), intent(out) :: buf
integer :: num_chars_read
! Your code here
num_chars_read = 0
end function read
end program maintemp.f95:29:54:
29 | function read(file, n, buf) result(num_chars_read)
| 1
Error: FUNCTION attribute conflicts with SUBROUTINE attribute in ‘read’ at (1)
temp.f95:30:21:
30 | implicit none
| 1
Error: Unexpected IMPLICIT NONE statement in CONTAINS section at (1)
temp.f95:31:44:
31 | character(len=*), intent(in) :: file
| 1
Error: Unexpected data declaration statement in CONTAINS section at (1)
temp.f95:32:32:
32 | integer, intent(in) :: n
| 1
Error: Unexpected data declaration statement in CONTAINS section at (1)
temp.f95:33:44:
33 | character(len=*), intent(out) :: buf
| 1
Error: Unexpected data declaration statement in CONTAINS section at (1)
temp.f95:34:33:
34 | integer :: num_chars_read
| 1
Error: Unexpected data declaration statement in CONTAINS section at (1)
temp.f95:37:26:
37 | num_chars_read = 0
| 1
Error: Unexpected assignment statement in CONTAINS section at (1)
temp.f95:38:7:
38 | end function read
| 1
Error: Expecting END PROGRAM statement at (1)
! Declare variables
integer :: n, i, j, k, l, m, read4_return
character(len=4) :: buf4
character(len=1000) :: file
character(len=1000) :: buf
! Read the value of n
read(*,*) n
! Initialize variables
i = 1
j = 1
k = 1
l = 1
m = 1
! Read the contents of the file
do while (i <= n)
! Read 4 characters from the file
read4_return = read4(buf4)
! Check if the end of the file has been reached
if (read4_return == 0) then
exit
end if
! Copy the 4 characters to the buffer
do while (j <= read4_return)
buf(k:k) = buf4(j:j)
k = k + 1
j = j + 1
end do
! Increment the file pointer
i = i + 4
end do
! Print the contents of the buffer
write(*,*) buf(1:k-1)
end
! Read4 method
function read4(buf4) result(read4_return)
! Declare variables
integer :: i, j, k, l, m, read4_return
character(len=4) :: buf4
! Initialize variables
i = 1
j = 1
k = 1
l = 1
m = 1
! Read 4 characters from the file
read4_return = read(l:l)
! Check if the end of the file has been reached
if (read4_return == 0) then
exit
end if
! Copy the 4 characters to the buffer
do while (j <= read4_return)
buf4(k:k) = read4_return
k = k + 1
j = j + 1
end do
! Increment the file pointer
l = l + 1
end function read4
temp.f95:58:22:
58 | read4_return = read(l:l)
| 1
Error: Syntax error in argument list at (1)
temp.f95:62:8:
62 | exit
| 1
Error: EXIT statement at (1) is not within a construct
temp.f95:67:16:
67 | buf4(k:k) = read4_return
| 1
Error: Cannot convert INTEGER(4) to CHARACTER(0) at (1)
temp.f95:20:24:
20 | read4_return = read4(buf4)
| 1
Error: Return type mismatch of function ‘read4’ at (1) (REAL(4)/INTEGER(4))
def read4(buf4: List[str]) -> int:
pass
def read(buf: List[str], n: int) -> int:
total_read = 0
buf4 = [''] * 4
while total_read < n:
read4_count = read4(buf4)
for i in range(read4_count):
if total_read < n:
buf[total_read] = buf4[i]
total_read += 1
else:
break
if read4_count < 4:
break
return total_read
The algorithm relies on the read4 function provided, which reads 4 characters at a time. We read and store these characters in a buffer (buf4) and then transfer them one by one into the destination buffer (buf) until we reach the desired number of characters (n). We repeat this process until we have read n characters or reached the end of the file. If we reach the end of the file, the read4 function will return less than 4 characters, which is detected and used to break the loop.
In each language, we declare a buffer buf4 of length 4 to store the characters read using the read4 function. We keep track of the total characters read (totalRead) and iterate through the characters in buf4, transferring them one by one to the destination buffer buf. We make sure not to exceed the requested number of characters n.
Once we reach the end of the file, the read4 function will return less than 4 characters. If this happens, we break the loop and return the total number of characters read, which is stored in totalRead.
int read4(char *buf4);
int read(char *buf, int n) {
int totalRead = 0;
char buf4[4];
while (totalRead < n) {
int read4Count = read4(buf4);
for (int i = 0; i < read4Count && totalRead < n; ++i) {
buf[totalRead++] = buf4[i];
}
if (read4Count < 4) break;
}
return totalRead;
}
The algorithm relies on the read4 function provided, which reads 4 characters at a time. We read and store these characters in a buffer (buf4) and then transfer them one by one into the destination buffer (buf) until we reach the desired number of characters (n). We repeat this process until we have read n characters or reached the end of the file. If we reach the end of the file, the read4 function will return less than 4 characters, which is detected and used to break the loop.
In each language, we declare a buffer buf4 of length 4 to store the characters read using the read4 function. We keep track of the total characters read (totalRead) and iterate through the characters in buf4, transferring them one by one to the destination buffer buf. We make sure not to exceed the requested number of characters n.
Once we reach the end of the file, the read4 function will return less than 4 characters. If this happens, we break the loop and return the total number of characters read, which is stored in totalRead.