157. Read N Characters Given Read4
- Total Accepted: 19570
- Total Submissions: 66588
- Difficulty: Easy
- Contributors: Admin
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.
Code
# The read4 API is already defined for you.
# @param buf, a list of characters
# @return an integer
# def read4(buf):
class Solution(object):
def read(self, buf, n):
"""
:type buf: Destination buffer (List[str])
:type n: Maximum number of characters to read (int)
:rtype: The number of characters read (int)
"""
idx = 0
while True:
if idx == n:
return idx
buf4 = [0]*4
read4_ret = read4(buf4)
for i in xrange(read4_ret):
if idx < n:
buf[idx] = buf4[i]
idx += 1
else:
return idx
if read4_ret < 4:
return idx
Idea
You read contents into buf. You should create a small buffer buf4 to save contents from read4. Then, based on how many characters you have read, determine when to return.