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_158.java
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package com.fishercoder.solutions;
/**
158. Read N Characters Given Read4 II - Call multiple times
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.
Example 1:
Given buf = "abc"
read("abc", 1) // returns "a"
read("abc", 2); // returns "bc"
read("abc", 1); // returns ""
Example 2:
Given buf = "abc"
read("abc", 4) // returns "abc"
read("abc", 1); // returns ""
*/
public class _158 {
public static class Solution1 {
/**
* @param buf Destination buffer
* @param n Maximum number of characters to read
* @return The number of characters read
*/
private int buffPtr = 0;
private int buffCnt = 0;
private char[] buff = new char[4];
public int read(char[] buf, int n) {
int ptr = 0;
while (ptr < n) {
if (buffPtr == 0) {
buffCnt = read4(buff);
}
if (buffCnt == 0) {
break;
}
while (ptr < n && buffPtr < buffCnt) {
buf[ptr++] = buff[buffPtr++];
}
if (buffPtr >= buffCnt) {
buffPtr = 0;
}
}
return ptr;
}
//This is a fake method to make IDE happy.
private int read4(char[] buff) {
return 1;
}
}
}