编程实现lzw编码解码.docx

1、编程实现lzw编码解码江苏大学计算机与通信工程学院实验报告 实验：编程实现lzw编码解码学号： 姓名：指导老师：日期：1任务说明对由a,b,c,d构成的字符进行LZW编码，然后译码。2问题分析、实现原理、流程图由于时间有不多，不想用4叉树。就用简单直接的单链表实现字典。虽然效率极低，但长度小于100，所以没有太大问题。1.字典初始化：建立4个节点a,b,c,d;2.动态数据初始化:当发现字典中没有的，就把它加入字典。3.结束判断如果文件再无输入字符了，输出当前单词W的序号（即S的序号），编码结束。3实现源码#include#include #define MAXLEN 10000typedef

2、 struct Node /* 定义单链表结点类型 */ char *pstr; unsigned num; Node *next;Node;int appendNode(Node *head,char *pstr);int getNum(Node *head,char *pstr);int freelist(Node *head);char *search(Node *head,int num);Node *getLastNode(Node *head);int main() char bufferMAXLEN; FILE *fpin,*fpout; int i=0,ch; Node *he

3、ader; int slen,encodelen=0; /read data fopen_s(&fpin,in4.txt,r); fopen_s(&fpout,out4.txt,w+); if (fpin=NULL) printf(open file errorn); return 0; ch = fgetc( fpin ); for( slen=0; (slen next=NULL; header-num=0; header-pstr=NULL; appendNode(header,a); appendNode(header,b); appendNode(header,c); appendN

4、ode(header,d); char x2=0,IMAXLEN=0; int currentNum,temp; I0=buffer0; while (1) static int i=0; temp=getNum(header,I); if (temp = 0) encodeencodelen+=currentNum; int ret=appendNode(header,I); printf(%d %sn,ret,I); memset(I,0,4*sizeof(char); I0=x0; else currentNum=temp; x0=buffer+i; if (x0d) /到达末尾 pri

5、ntf(%7dn,currentNum); encodeencodelen+=currentNum; break; strcat(I,x); freelist(header); printf_s(encode: n); fprintf_s(fpout,n编码为：n); for (int i=0;i+) /输出编码 if (encodei=0) break; printf_s(%d ,encodei); fprintf_s(fpout,%d ,encodei); printf(n); fprintf_s(fpout,n原文：%sn,buffer); /译码 fprintf_s(fpout,n还原

6、为：); header=new Node; header-next=NULL; header-num=0; header-pstr=NULL; appendNode(header,a); appendNode(header,b); appendNode(header,c); appendNode(header,d); memset(I,0,16); char *pword; Node *tempNode; for (int i=0;i0) /setx x0=pword0; tempNode = getLastNode(header); strcat(tempNode-pstr,x); prin

7、tf(pword); fprintf_s(fpout,%s,pword); appendNode(header,pword); /存字典 printf_s(n原始码长：%d,编码长：%dn 压缩率为:%f,slen,encodelen,encodelen/(float)slen); fprintf_s(fpout,n原始码长：%d,编码长：%dn %d/%d = %f,slen,encodelen,encodelen,slen,encodelen/(float)slen); fclose(fpout); getchar(); return 0;int appendNode(Node *head

8、,char *pstr) int i=1; Node *p=head,*temp; while (p-next) i+; p=p-next; temp=new Node; temp-next=NULL; temp-num=i; temp-pstr=new charstrlen(pstr)+1; strcpy_s(temp-pstr,strlen(pstr)+1,pstr); p-next=temp; return i;int getNum(Node *head,char *pstr) int i=0,flag=0; Node *p=head; while (p-next) p=p-next;

9、i+; if (0=strcmp(p-pstr,pstr) flag=1; break; if (flag=1) return i; /no this node return 0;int freelist(Node *head) Node *temp; while (head) temp = head; head=head-next; delete temp-pstr; delete temp; return 0;char * search(Node *header,int num) Node *p=header; int i=0; while (i!=num)&(p) p=p-next; i

10、+; return p-pstr;Node *getLastNode(Node *head) Node *p=head; while (p-next) p=p-next; return p;4运行结果：输入、输出及结果分析待编码( int4.txt )：abdcacadcadbdadcdadbcbcabdacbdcadbcabdcabdcaddabcbadbacdcadbacdbacdcadacdacdacdddcadbadbcbdacbdadadadcbdabcdacadcdacddbcdbcadbcdbcdbacbdacbdacbddabdcbdabcdabcdabcdbcdabcdabc

11、dacbdacbdadacdcdbacdbcabdacbdadcdacdabdaabdcacdbcadacdacdcdababddabdaddcdadcabadcbddcdbadcdadbaccadacabcadb输出（out4.txt）：编码为：1 2 4 3 1 8 7 1 4 6 12 3 4 12 2 3 19 5 17 20 11 13 8 6 27 25 17 19 2 18 9 25 33 16 37 25 35 41 16 4 36 18 24 9 14 17 50 47 19 23 15 23 44 53 21 26 60 37 14 47 24 31 7 14 53 5 1

12、6 70 60 72 74 64 49 35 38 35 21 63 49 71 71 14 22 8 38 10 42 7 31 22 66 12 92 15 5 15 6 92 33 97 13 9 90 27 10 2 原文：abdcacadcadbdadcdadbcbcabdacbdcadbcabdcabdcaddabcbadbacdcadbacdbacdcadacdacdacdddcadbadbcbdacbdadadadcbdabcdacadcdacddbcdbcadbcdbcdbacbdacbdacbddabdcbdabcdabcdabcdbcdabcdabcdacbdacbdad

13、acdcdbacdbcabdacbdadcdacdabdaabdcacdbcadacdacdcdababddabdaddcdadcabadcbddcdbadcdadbaccadacabcadb还原为：abdcacadcadbdadcdadbcbcabdacbdcadbcabdcabdcaddabcbadbacdcadbacdbacdcadacdacdacdddcadbadbcbdacbdadadadcbdabcdacadcdacddbcdbcadbcdbcdbacbdacbdacbddabdcbdabcdabcdabcdbcdabcdabcdacbdacbdadacdcdbacdbcabdacbdadcdacdabdaabdcacdbcadacdacdcdababddabdaddcdadcabadcbddcdbadcdadbaccadacabcadb原始码长：280,编码长：106 106/280 = 0.3785715设计体会虽然没用4叉树，后来思考了下，用4叉树可能更简单，但通过实验对lzw编码方法有了基本了解。lzw设计的很巧妙。