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1、用思维导图和实例学习C 之一 字符串处理1.本章思维导图：Example1：char*strcpy(char*target,const char*source)char*t=target；/Copy the contents of source into target.while(*source)*target+=*source+；/Null-terminate the target.*target=message；/Return pointer to the start of target.return t；Example2：void*memmove(void*target,const vo
2、id*source,size_t count)这个函数即使是在源和目的字符串有所重叠时操作也能成功，虽然source为const，但是其指向的array也可能被修改。2.C型字符串操作实例：Ex1.基本操作/*=*Filename：2-1.cpp*Description：Fundamental Operations in CType String*Version：1.0*Created：05/11/2010 10：43：11 AM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include usin
3、g namespace std；int main(int argc,char*argv)char strA7=UP；char strB5=DOWN；char strC5=LEFT；char strD6=RIGHT；/*Display*/coutHere are the strings：endl；coutstrA：strA endl；coutstrB：strB endl；coutstrC：strC endl；coutstrD：strDnn；/Display the length of strA.coutLength of strA isstrlen(strA)endl；coutSize of s
4、trA issizeof(strA)endl；/Concatenate strB with strA coutThe result of Concatenate is strA：/Copy strC into strB,and partially strD into strA coutThe result of Copy is：coutThe result of partially Copy is strA：/Compare strC with strB if(！strcmp(strC,strB)coutstrC is equal to strB！if(！strncmp(strD,strA,3
5、)coutstrD is equal to strA partially！return 0；Ex2.搜索匹配相关操作/*=*Filename：2-2.cpp*Description：Search Operation in Ctype String*Version：1.0*Created：05/11/2010 11：38：15 AM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include using namespace std；int main(void)const char*url=HerbS；
6、const char*url2=Apache.org；const char*emailaddr=HerbHerbS；const char*tld=.com,.net,.org；const char*p；/First,determine if url and url2 ,.net,or.org.for(int i=0；i 3；i+)p=strstr(url,tldi)；if(p)cout urlhas top-level domaintldiendl；p=strstr(url2,tldi)；if(p)cout url2has top-level domaintldiendl；/Search fo
7、r aspecific character.p=strchr(emailaddr,)；if(p)coutSite name of e-mail address is：p+1 endl；/Search for any of aset of characters.In this case,/find the firstor period.p=strpbrk(emailaddr,.)；if(p)coutFound*p endl；/Search for the beginning if(strspn(url2,Apache)=6)coutUrl2 begins with theApacheendl；/
8、与strchr正好倒过来if(p=strrchr(emailaddr,b)cout pendl；return 0；Ex3.倒置一个字符串我们用了四种方法，最后一种方法经常在面试笔试题中出现。/*=*Filename：2-3.cpp*Description：Reverse astring*Version：1.0*Created：05/12/2010 03：08：09 PM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include using namespace std；void revstr(cha
9、r*str)；void revstr_p(char*str)；void revstr_recursive(char*str,int start,int end)；char*(revstrcpy)(char*rstr,const char*orgstr)；int main()char str=abcdefghijklmnopqrstuvwxyz；char*des=new char27；coutOriginal string：str endl；revstr(str)；coutReversed string：str endl；revstr_p(str)；coutReversed string usi
10、ng pointer：str endl；revstr_recursive(str,0,strlen(str)-1)；coutReversed string using recursive：str endl；coutReversed string using copy method：revstrcpy(des,str)endl；return 0；void revstr(char*str)int i,j；char t；for(i=0,j=strlen(str)-1；i j；+i,-j)t=stri；stri=strj；strj=t；/Reverse astring in place.Use poi
11、nters rather than array indexing.void revstr_p(char*str)char t；char*inc_p=str；char*dec_p=&strstrlen(str)-1；while(inc_p=dec_p)t=*inc_p；*inc_p+=*dec_p；*dec_p-=t；void revstr_recursive(char*str,int start,int end)if(start end)revstr_recursive(str,start+1,end-1)；else return；char t=strstart；strstart=strend
12、；strend=t；char*(revstrcpy)(char*rstr,const char*orgstr)/返回rstr的原始值使函数能够支持链式表达式，增加了函数的附加值。同样功能的函数，如果能合理地提高的可用性，自然就更加理想。if(rstr=NULL)|(orgstr=NULL)throwInvalid argument(s)；char*dst=rstr；dst+=strlen(orgstr)；*dst-=message；while(*orgstr)*dst-=*orgstr+；return rstr；Ex4.忽略大小写的字符串比较/*=*Filename：2-4.cpp*Descr
13、iption：Ignore the Letter case when compared*Version：1.0*Created：05/12/2010 03：44：34 PM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include using namespace std；int strcmp_ign_case(const char*str1,const char*str2)；int main(void)char strA=tesT；char strB=Test；char strC=testing；
14、char strD=Tea；int result；coutHere are the strings：endl；coutstrA：strA endl；coutstrB：strB endl；coutstrC：strC endl；coutstrD：strDnn；/Compare strings ignoring case.result=strcmp_ign_case(strA,strB)；result=strcmp_ign_case(strA,strC)；result=strcmp_ign_case(strA,strD)；result=strcmp_ign_case(strD,strA)；retur
15、n 0；/A simple string comparison function that ignores case differences.int strcmp_ign_case(const char*str1,const char*str2)const char*str1_cp=str1；const char*str2_cp=str2；while(*str1_cp&*str2_cp)if(tolower(*str1_cp+)！=tolower(*str2_cp+)break；int result=tolower(*str1_cp)-tolower(*str2_cp)；cout str1is
16、；if(！result)coutequal to；else if(result 0)coutless than；else coutgreater than；cout str2 endl；return result；Ex5.搜索替换/*=*Filename：2-5.cpp*Description：Replace the sub_str with another str*Version：1.0*Created：05/12/2010 04：07：02 PM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#in
17、clude#include using namespace std；bool search_and_replace(char*orgstr,int maxlen,const char*oldsubstr,const char*newsubstr)；char*search_and_replace_alloc(const char*str,const char*oldsubstr,const char*newsubstr)throw(bad_alloc)；int main(void)char str80=alpha beta gamma alpha beta gamma；char*ptr=NULL
18、；coutOriginal string：strnn；coutFirst,replace all instances of alpha with epsilon.n；/Replace all occurrences of alpha with epsilon.while(search_and_replace(str,sizeof(str),alpha,epsilon)coutAfter areplacement：str endl；coutSecond,replace one instances of epsilon with alpha.n；tryptr=search_and_replace_
19、alloc(str,epsilon,alpha)；catch(bad_alloc exc)/Take appropriate action here.if(ptr)coutAfter areplacement：ptr endl；delete ptr；return 0；bool search_and_replace(char*orgstr,int maxlen,const char*oldsubstr,const char*newsubstr)char*pos=NULL；if(orgstr=NULL)|(oldsubstr=NULL)|(newsubstr=NULL)return false；i
20、nt len=strlen(orgstr)-strlen(oldsubstr)+strlen(newsubstr)；if(len maxlen)return false；if(pos=strstr(orgstr,oldsubstr)memmove(pos+strlen(newsubstr),pos+strlen(oldsubstr),strlen(pos)-strlen(oldsubstr)+1)；strncpy(pos,newsubstr,strlen(newsubstr)；return true；elsereturn false；char*search_and_replace_alloc(
21、const char*str,const char*oldsubstr,const char*newsubstr)throw(bad_alloc)const char*pos=NULL；if(str=NULL)|(oldsubstr=NULL)|(newsubstr=NULL)return NULL；int size=strlen(str)+strlen(newsubstr)-strlen(oldsubstr)+1；char*result=new charsize；if(pos=strstr(str,oldsubstr)strncpy(result,str,pos-str)；*(result+
22、(pos-str)=message；strcat(result,newsubstr)；strcat(result,pos+strlen(oldsubstr)；cout return result；elsedelete result；return NULL；Ex6.文本统计/*=*Filename：2-6.cpp*Description：Text statistics Function*Version：1.0*Created：05/13/2010 02：37：34 PM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#i
23、nclude#include using namespace std；struct wc/不使用class是因为这是一个纯数据的对象，虽然它包含一个默认的构造函数。int words；int spaces；int punct；int lines；wc()words=punct=spaces=lines=0；wc wordcount(const char*str)；int main()const char*test=By supplying astring class and alsosupporting null-terminated strings,nC+offers arich progr
24、amming environment forstring-intensive tasks.nIts power programming.；coutGiven：nn；cout test endl；wc wcd=wordcount(test)；coutnWords：wcd.words endl；coutSpaces：wcd.spaces endl；coutLines：wcd.lines endl；coutPunctuation：wcd.punct endl；return 0；wc wordcount(const char*str)wc data；if(*str)+data.lines；while(
25、*str)if(isalpha(*str)while(isalpha(*str)|*str=)if(*str=)+data.punct；+str；data.words+；elseif(ispunct(*str)+data.punct；else if(isspace(*str)+data.spaces；if(*str=n&*(str+1)+data.lines；+str；return data；Ex7解析一个C型字符串/*=*Filename：2-7.cpp*Description：String Token*Version：1.0*Created：05/14/2010 10：01：58 AM*R
26、evision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include using namespace std；#define MAX_TOKEN_SIZE 128 const char*gettoken(const char*str)；int main()char delims=.,?；！；char str=I like apples,pears,and grapes.Do you?；char*tok；coutObtain the words in asentence.n；tok=strtok(str,deli
27、ms)；while(tok)cout tok endl；tok=strtok(NULL,delims)；char kvpairs=count=10,name=Tom Jones,jr.,max=100,min=0.01；char kvdelims=,；coutnTokenize key/Value pairs.n；tok=strtok(kvpairs,kvdelims)；while(tok)coutKey：tok；if(！strcmp(name,tok)tok=strtok(NULL,)；elsetok=strtok(NULL,kvdelims)；coutValue：tok endl；tok=
28、strtok(NULL,kvdelims)；coutOri String iskvpairs/We want to token the count,12 and the symbol add(+),but we cannot make it via strtok char count=max=12+3/89；count27=19*(min+floor)；char countdelims=+；const char*strtok=gettoken(count)；while(strtok)cout strtok endl；strtok=gettoken(NULL)；coutnn；return 0；c
29、onst char*gettoken(const char*str)static char tokenMAX_TOKEN_SIZE+1；/static makes the return method can be made.static const char*ptr；/static type holds the string last time passed in int count=0；/holds the current character count char*tokptr=token；if(str)ptr=str；while(isspace(*ptr)ptr+；if(isalpha(*
30、ptr)while(isalpha(*ptr)|isdigit(*ptr)*tokptr+=*ptr+；+count；if(count=MAX_TOKEN_SIZE)break；else if(isdigit(*ptr)while(isdigit(*ptr)*tokptr+=*ptr+；+count；if(count=MAX_TOKEN_SIZE)break；else if(ispunct(*ptr)*tokptr+=*ptr+；else return NULL；/Null terminate the token.*tokptr=message；return token；3.String操作实
31、例：Ex8 String基本操作/*=*Filename：2-8.cpp*Description：String Basic Operation*Version：1.0*Created：05/14/2010 02：15：06 PM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include using namespace std；int main()/Create some string objects.Three are initialized/using the string literal pa
32、ssed as an argument.string str1(Alpha)；string str2(Beta)；string str3(Gamma)；string str4；/Output astring via cout.coutHere are the original strings：n；coutstr1：str1 endl；coutstr2：str2 endl；coutstr3：str3nn；/Display the maximum string length.coutThe maximum string length is：str1.max_size()nn；/Display th
33、e size of str1.You can use length()instead.这两个方法其实是一个效果，有size只是为了满足兼容STL的要求coutstr1 containsstr1.size()characters.n；/Display the capacity of str1.coutCapacity of str1：str1.capacity()nn；/Display the characters in astring one at atime/by using the indexing operator.for(unsigned i=0；i str1.size()；+i)co
34、utstr1：str1iendl；/使用at方法也可以cout endl；/Assign one string to another.str4=str1；coutstr4 after being assigned str1：str4nn；/Concatenate two strings.str4=str1+str3；coutstr4 after begin assigned st1+str3：str4nn；/Insert one string into another.str4.insert(5,str2)；coutstr4 after inserting str2：str4nn；/Obtai
35、n asubstring.str4=str4.substr(5,4)；coutstr4 after being assigned str4.substr(5,4)：str4nn；/Compare two strings.coutCompare strings.n；if(str3 str1)coutstr3 str1n；/使用compare方法能够更加强大的比较String if(str3=str1+str2)coutstr3=str1+str2n；if(str1=str2)coutstr1=str2nn；/Create astring object using another string o
36、bject.coutInitialize str5 with the contents of str1.n；string str5(str1)；coutstr5：str5nn；/Erase str4.coutErasing str4.n；str4.erase()；/使用clear方法也可以if(str4.empty()coutstr4 is now empty.n；coutSize and capacity of str4 isstr4.size()str4.capacity()nn；/Use push_back()to add characters to str4.for(char ch=A
37、；ch=Z；+ch)str4.push_back(ch)；coutstr4 after calls to push_back()：str4 endl；coutSize and capacity of str4 is nowstr4.size()str4.capacity()nn；/Set the capacity of str4 to 128.coutSetting the capacity of str4 to 128n；str4.reserve(128)；coutCapacity of str4 is now：str4.capacity()nn；/Input astring via cin
38、.coutEnter astring：；cin str1；coutYou entered：str1nn；return 0；Ex9搜索操作/*=*Filename：2-9.cpp*Description：Search String*Version：1.0*Created：05/14/2010 03：16：12 PM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include using namespace std；void showresult(string s,string：size_type i)
39、；int main()string：size_type indx；/这是很标准的使用方法，而不是使用int或者unsigned int/Create astring.string str(one two three,one two three)；string str2；coutString to be searched：strnn；coutSearching for the first occurrence oftwon；indx=str.find(two)；showresult(str,indx)；coutSearching for the last occurrence oftwon；in
40、dx=str.rfind(two)；showresult(str,indx)；coutSearching for the first occurrence of tor hn；indx=str.find_first_of(th)；showresult(str,indx)；coutSearching for the last occurrence of tor hn；indx=str.find_last_of(th)；showresult(str,indx)；coutSearching for the first occurrence of any character otherthan o,n
41、,e,or spacen；indx=str.find_first_not_of(one)；showresult(str,indx)；coutSearching for the last occurrence of any character otherthan o,n,e or spacen；indx=str.find_last_not_of(one)；showresult(str,indx)；return 0；/Display the results of the search.void showresult(string s,string：size_type i)if(i=string：n
42、pos)/在没有匹配的部分都是返回npos coutNo match found.n；return；coutMatch found at indexi endl；coutRemaining string from point of match：s.substr(i)nn；Ex10.搜索替换操作：这个版本比C型字符串要简单许多，主要原因是String的动态特性和/*=*Filename：2-11.cpp*Description：String Search and Replace*Version：1.0*Created：05/14/2010 03：48：47 PM*Revision：none*Co
43、mpiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include using namespace std；bool search_and_replace(string&str,const string&oldsubstr,const string&newsubstr)；int main()string str=This is atest.So is this.；coutOriginal string：strnn；coutReplacingiswithwas：n；/The following replaces is with was.No
44、tice that/it passes string literals for the substrings./These are automatically converted into string objects.while(search_and_replace(str,is,was)cout str endl；cout endl；/Of course,you can explicitly pass string objects,too.string oldstr(So)；string newstr(So too)；coutReplaceSowithSo tooendl；search_a
45、nd_replace(str,oldstr,newstr)；cout str endl；return 0；bool search_and_replace(string&str,const string&oldsubstr,const string&newsubstr)string：size_type startidx；startidx=str.find(oldsubstr)；if(startidx！=string：npos)str.replace(startidx,oldsubstr.size(),newsubstr)；return true；return false；Ex11.迭代器的基本使用/*=*Filename：2-13.cpp*Description：String Iterator*Version：1.0*Created：05/14/2010 04：55：41 PM*Revision：none*Compiler：gcc*Author：gnuhpc(*Company：IBM CDL*=*/#include#include#include#include#include using namespace std；int main()string strA(This is atest.)；/Create an iter