Description
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.
Example 1:
Input: buf ="abc", n = 4
Output: "abc"
Explanation: The actual number of characters read is 3, which is "abc".
Example 2:
Input: buf = "abcde", n = 5
Output: "abcde"
Note:
The read function will only be called once for each test case.
Solution
考虑下面两种情况：
- buf不够长
- file不够长
/* 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) {
char[] tmp = new char[4];
int i = 0;
while (i < n) {
int count = read4(tmp);
for (int k = 0; k < count && i < n; ++k) {
buf[i++] = tmp[k];
}
if (count < 4) { // file ended
break;
}
}
return i;
}
}
