第四次作业
1、 参考书《数据压缩导论(第4版)》 Page 121
7、使用LZ77算法对一个序列进行编码。给定C(a)=1,C(p)=2,C(r)=3,C(t)=5。对一下三组序列进行解码:
<0,0,3><0,0,1><0,0,4><2,8,2><3,1,2><0,0,3><6,4,4><9,5,4>
假设窗口的大小为20,先行缓冲区的大小为10.对解码所得的序列进行编码,确保得到相同的三元组序列。
解:窗口大小为20,先行缓冲区大小为10。
C(a) = 1, C(p ) = 2, C(r) = 3, C(t) = 4
解码过程:
输入 | 输出 |
<0, 0, 3> | r |
<0, 0, 1> | ra |
<0, 0, 4> | rat |
<2, 8, 2> | ratatatatat |
<3, 1, 2> | ratatatatat a |
<0, 0, 3> | ratatatatat a r |
<6, 4, 4> | ratatatatat a rat at |
<9, 5, 4> | ratatatatat a rat at a rat |
编码过程:输入序列:ratatatatat a rat at a rat
输入 | 输出 |
||ratatatatat a rat at a rat | <0, 0, 3> |
|r|atatatatat a rat at a rat | <0, 0, 1> |
|ra|tatatatat a rat at a rat | <0, 0, 4> |
|rat|atatatat a rat at a rat | <2, 8, 2> |
ra|tatatatat |a rat at a rat | <3, 1, 2> |
rata|tatatat a |rat at a rat | <0, 0, 3> |
ratat|atatat a r|at at a rat | <6, 4, 4> |
ratatatata|t a rat at|a rat | <9, 5, 4> |
编码输出的三元组与解码输入的三元组完全一样。
8、给定以下初始词典和接收序列,构建一个LZW词典,并对所发送的序列进行编码。
接收序列:4,5,3,1,2,8,7,9,7,4
初始词典:
索引 | 项 |
1 | S |
2 | P |
3 | I |
4 | T |
5 | H |
答案:
接收到的序列:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:T
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:TH
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THI
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
7 |
HI |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
7 |
HI |
8 |
IS |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
7 |
HI |
8 |
IS |
9 |
S |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS IS
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
7 |
HI |
8 |
IS |
9 |
S |
10 |
I |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS IS
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
7 |
HI |
8 |
IS |
9 |
S |
10 |
I |
11 |
IS |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS IS HI
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
7 |
HI |
8 |
IS |
9 |
S |
10 |
I |
11 |
IS |
12 |
H |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS IS HIS
1 |
S |
2 |
|
3 |
I |
4 |
T |
5 |
H |
6 |
TH |
7 |
HI |
8 |
IS |
9 |
S |
10 |
I |
11 |
IS |
12 |
H |
13 |
HIS |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS IS HIS HI
1 |
S |
2 |
|
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 |
输入:4, 5, 3, 1, 2, 8, 2, 7, 9, 7, 4
字典: 解码出的序列:THIS IS HIS HIT
1 |
S |
2 |
|
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 |
15 |
HIT |