05 August 2008
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/**
* The read4 API is defined in the parent class Reader4.
* int read4(char[] buf4);
*/
public class Solution extends Reader4 {
/**
* @param buf Destination buffer
* @param n Number of characters to read
* @return The number of actual characters read
*/
char[] bufCache = new char[4];
int bufPtr = 0;
int bufCount = 0;
public int read(char[] buf, int n) {
int nIndex = 0;
// fill out every position until reach n
while (nIndex < n) {
// only if bufPtr does not reach the end of bufCache array, we can assign value from bufCache to final buf array
if (bufPtr < bufCount) {
buf[nIndex++] = bufCache[bufPtr++];
}
// if we already used all characters from bufCache, we need to read new characters by calling read4()
// and then fill the bufCache
else {
bufCount = read4(bufCache);
bufPtr = 0;
// if no more characters we can read, we should break the entire loop and return 0
if (bufCount == 0) {
break;
}
}
}
return nIndex;
}
}
解法2，利用额外空间queue 158 Read N Characters Given Read4 II - Call multiple times