157. Read N Characters Given Read4

Solution.java

/**
 * 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   Number of characters to read
     * @return    The number of actual characters read
     */
    public int read(char[] buf, int n) {
        // System.out.printf("Initial buffer: %s\n", Arrays.toString(buf));
        int insertionIndex = 0;
        int remainingChars = n - insertionIndex;
        char[] buffer = new char[4];
        boolean reachedEnd = false;
        while (!reachedEnd && remainingChars > 0) {
            int charsRead = read4(buffer);
            // System.out.printf("Read %d chars into buffer: %s\n", charsRead, Arrays.toString(buffer));
            if (charsRead < 4) {
                reachedEnd = true;
            }
            int charsToWrite = remainingChars < charsRead ? remainingChars : charsRead;
            for (int i = 0; i < charsToWrite; i++, insertionIndex++) {
                buf[insertionIndex] = buffer[i];
            }
            remainingChars = n - insertionIndex;
            // System.out.printf("insertionIndex: %d\tremainingChars: %d\treachedEnd: %b\tResult buffer: %s\n", insertionIndex, remainingChars, reachedEnd, Arrays.toString(buf));
        }
        return insertionIndex;
    }
}