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 may be called multiple times.
1 /* The Read4 API is defined in the parent class Reader4. 2 int Read4(char[] buf); */ 3 4 public class Solution : Reader4 { 5 /** 6 * @param buf Destination buffer 7 * @param n Maximum number of characters to read 8 * @return The number of characters read 9 */ 10 11 private Queue<char> buffer = new Queue<char>(); 12 13 public int Read(char[] buf, int n) { 14 // try to read from buffer 15 int i = 0; 16 while (i < n && buffer.Count > 0) 17 { 18 buf[i++] = buffer.Dequeue(); 19 } 20 21 // try to read from file 22 bool eof = false; 23 while (i < n && !eof) 24 { 25 var temp = new char[4]; 26 int r = Read4(temp); 27 28 if (r < 4) 29 { 30 eof = true; 31 } 32 33 for (int k = 0; k < r; k++) 34 { 35 if (i >= n) 36 { 37 // save the left into the buffer 38 buffer.Enqueue(temp[k]); 39 } 40 else 41 { 42 buf[i++] = temp[k]; 43 } 44 } 45 } 46 47 return i; 48 } 49 }
