题目:
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.
解答:
读懂题目很重要,还是要多写写这种实际的api的问题。
/* 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) {
boolean end = false;
int total = 0;
char[] temp = new char[4];
//有两种情况:1. 需要read的character个数是n,但实际文件中character个数小于n个,所以我们只能返回实际character的个数;2. 需要read的character个数n小于实际文件中的个数,所以最后一步只需要n - total个character就可以。
while (!end && total < n) {
int count = read4(temp);
//实际文件读到头了的情况
end = count < 4;
//需要读的文件个数达到了的情况
count = Math.min(count, n - total);
for (int i = 0; i < count; i++) {
buf[total++] = temp[i];
}
}
return total;
}
}
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