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.
Python Solution:
# 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)
"""
_buf = [""] * 4
res = 0
while n:
_n = read4(_buf)
if not _n: break
_len = min(_n, n)
for i in range(_len):
buf[res] = _buf[i]
res += 1
n -= _n
return res
C++ Solution:
// Forward declaration of the read4 API.
int read4(char *buf);
class Solution {
public:
/**
* @param buf Destination buffer
* @param n Maximum number of characters to read
* @return The number of characters read
*/
int read(char *buf, int n) {
char _buf[4];
int res = 0;
while (n) {
int _n = read4(_buf);
if (!_n) break;
_n = _n < n ? _n : n;
int i;
for (i = 0; i < _n; i++) buf[res++] = _buf[i];
n -= _n;
}
return res;
}
};
Summary:
- This problem really should not be solved with Python.
LeetCode: 157. Read N Characters Given Read4
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