157. Read N Characters Given Read4

主要是看懂题。。
用给你提供的read4去实现readN，是这个意思。。

/* 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) 
    {
        int res = 0;
        
        while(res < n)
        {
            char[] temp = new char[4];
            int a = read4(temp);
            int b = 0;
            
            while(a > 0 && res < n)
            {
                buf[res++] = temp[b++];
                a--;
                
            }
            
            
            if(b < 4) break;            
            
            
        }
        
        return res;
    }
}