第四次作业
参考书《数据压缩导论（第4版）》 Page 121
解：(1)由于C(a)=1,C(b)=2,C(r)=3,C(t)=4,所以解码的结果如下：
| 序列 | 输出 |
| <0,0,3> | r |
| <0,0,1> | ra |
| <0,0,4> | rat |
| <2,8,2> | ratatatatatb |
| <3,1,2> | ratatatatatbab |
| <0,0,3> | ratatatatatbabr |
| <6,4,4> | ratatatatatbabratbat |
| <9,5,4> | ratatatatatbabratbatbabrat |
(2)由于窗口的大小为20，先行缓冲区的大小为10，所以编码如下：
输入ratatatatatbabratbatbabrat
| 输入 | 输出 |
| ||ratatatatatbabratbatbabrat | <0,0,3> |
| |r|atatatatatbabratbatbabrat | <0,0,1> |
| |ra|tatatatatbabratbatbabrat | <0,0,4> |
| |rat|atatatatbabratbatbabrat | <2,8,2> |
| ra|tatatatatb|abratbatbabrat | <3,1,2> |
| rata|tatatatbab|ratbatbabrat | <0,0,3> |
| ratat|atatatbabr|atbatbabrat | <6,4,4> |
| ratatatata|tbabratbat|babrat | <9,5,4> |
解：由于接收序列为：4,5,3,1,2,8,2,7,9,7,4；
所以输入序列为：4,5,3,1,2,8,2,7,9,7,4
1）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _(空格) |
| 3 | I |
| 4 | T |
| 5 | H |
解码的序列为：T
2）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
解码的序列为：TH
3）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _(空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
解码的序列为：THI
4）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
解码的序列为：THIS
5）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
| 8 | IS |
解码的序列为：THIS_
6）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
| 8 | IS |
| 9 | S_ |
解码的序列为：THIS IS
7）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
| 8 | IS |
| 9 | S_ |
| 10 | _I |
解码的序列为：THIS IS_
8）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
| 8 | IS |
| 9 | S_ |
| 10 | _I |
| 11 | IS_ |
解码的序列为：THIS IS HI
9）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
| 8 | IS |
| 9 | S_ |
| 10 | _I |
| 11 | IS_ |
| 12 | _H |
解码的序列为：THIS IS HIS_
10）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
| 8 | IS |
| 9 | S_ |
| 10 | _I |
| 11 | IS_ |
| 12 | _H |
| 13 | HIS |
解码的序列为：THIS IS HIS HI
11）输入4,5,3,1,2,8,2,7,9,7,4
| 索引 | 条目 |
| 1 | S |
| 2 | _ (空格) |
| 3 | I |
| 4 | T |
| 5 | H |
| 6 | TH |
| 7 | HI |
| 8 | IS |
| 9 | S_ |
| 10 | _I |
| 11 | IS_ |
| 12 | _H |
| 13 | HIS |
| 14 | S_H |
解码的序列为：THIS IS HIS HIT
综上可得：解码的序列为THIS IS HIS HIT。
