文本:abcacadbacdabaacbaba传统表示方法:a:00,b:01,c:10,d:11传统表示未压缩时:0001100010001101001011001000001001001000统计次数:a:9,b:5,c:4,d:2前缀码表示:a:0,b:10,c:110,d:111压缩后:0101100110011110011011101000110100100