c/c++ string

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 = '\0';
  // Return pointer to the start of target.
  return t;
}

Example2:
void *memmove(void *target, const void *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 C Type String
*
*        Version:  1.0
*        Created:  05/11/2010 10:43:11 AM
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/
#include 
#include 

using namespace std;

int main(int argc, char *argv[])
{
    char strA[7]="UP";
    char strB[5]="DOWN";
    char strC[5]="LEFT";
    char strD[6]="RIGHT";

    /*Display */
    cout << "Here are the strings: " << endl;
    cout << "strA: " << strA << endl;
    cout << "strB: " << strB << endl;
    cout << "strC: " << strC << endl;
    cout << "strD: " << strD << "\n\n";

    //Display the length of strA.
      cout << "Length of strA is " << strlen(strA) << endl;
      cout << "Size of strA is " << sizeof(strA) << endl;
    //Concatenate strB with strA
    cout << "The result of Concatenate is strA::" <<

    //Copy strC into strB,and partially strD into strA
    cout << "The result of Copy is:" <<
    cout << "The result of partially Copy is strA:" <<

    //Compare strC with strB
    if( !strcmp(strC,strB))
    {
        cout << "strC is equal to strB!"<
    }

    if( !strncmp(strD,strA,3))
    {
        cout << "strD is equal to strA partially!"<
    }

    return 0;

}

Ex2.搜索匹配相关操作

/*
* =====================================================================================
*
*       Filename:  2-2.cpp
*
*    Description:  Search Operation in C type String
*
*        Version:  1.0
*        Created:  05/11/2010 11:38:15 AM
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/

#include
#include
using namespace std;
int main(void) {
  const char *url = "HerbSchildt.com";
  const char *url2 = "Apache.org";
  const char *emailaddr = "Herb@HerbSchildt.com";
  const char *tld[] = { ".com", ".net", ".org" };
  const char *p;
  // First, determine if url and url2 contain .com, .net, or .org.
  for(int i=0; i < 3; i++) {
    p = strstr(url, tld[i]);
    if(p) cout << url << " has top-level domain " << tld[i] << endl;
    p = strstr(url2, tld[i]);
    if(p) cout << url2 << " has top-level domain " << tld[i] << endl;
  }
  // Search for a specific character.
  p = strchr(emailaddr, '@');
  if(p) cout << "Site name of e-mail address is: " << p+1 << endl;
  // Search for any of a set of characters. In this case,
  // find the first @ or period.
  p = strpbrk(emailaddr, "@.");
  if(p) cout << "Found " << *p << endl;

  //Search for the beginning
  if(strspn(url2,"Apache")==6){
    cout<< "Url2 begins with the \"Apache\""<< endl;
  }

  //与strchr正好倒过来
  if(p=strrchr(emailaddr, 'b')){
    cout<< p << endl;
  }
  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 a string
*
*        Version:  1.0
*        Created:  05/12/2010 03:08:09 PM
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/
#include
#include
using namespace std;
void revstr(char *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 char[27];
  cout << "Original string: " << str << endl;
  revstr(str);
  cout << "Reversed string: " << str << endl;
  revstr_p(str);
  cout << "Reversed string using pointer: " << str << endl;
  revstr_recursive(str,0,strlen(str)-1);
  cout << "Reversed string using recursive: " << str << endl;
  cout << "Reversed 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 = str[i];
    str[i] = str[j];
    str[j] = t;
  }
}

// Reverse a string in place. Use pointers rather than array indexing.
void revstr_p(char *str) {
  char t;
  char *inc_p = str;
  char *dec_p = &str[strlen(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 = str[start];
  str[start] = str[end];
  str[end] = 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))
      throw "Invalid argument(s)";

  char *dst=rstr;
  dst += strlen(orgstr);
  *dst-- = '\0';
  while(*orgstr)  *dst-- = *orgstr++; 
  return rstr;
}

Ex4. 忽略大小写的字符串比较

/*
* =====================================================================================
*
*       Filename:  2-4.cpp
*
*    Description:  Ignore the Letter case when compared
*
*        Version:  1.0
*        Created:  05/12/2010 03:44:34 PM
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        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";
  char strD[] = "Tea";
  int result;
  cout << "Here are the strings: " << endl;
  cout << "strA: " << strA << endl;
  cout << "strB: " << strB << endl;
  cout << "strC: " << strC << endl;
  cout << "strD: " << strD << "\n\n";
  // 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);
  return 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 << str1 << " is ";
  if(!result)
    cout << "equal to ";
  else if(result < 0)
    cout << "less than ";
  else 
    cout << "greater 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 (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/

#include
#include
#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 str[80] = "alpha beta gamma alpha beta gamma";
    char *ptr=NULL;
    cout << "Original string: " << str << "\n\n";
    cout << "First, replace all instances of alpha with epsilon.\n";
  // Replace all occurrences of alpha with epsilon.
    while(search_and_replace(str, sizeof(str), "alpha", "epsilon"))
        cout << "After a replacement: " << str << endl;
    cout << "Second, replace one instances of epsilon with alpha .\n";

    try {
      ptr = search_and_replace_alloc(str, "epsilon", "alpha");
    } catch(bad_alloc exc) {
      // Take appropriate action here.
    }
    if(ptr) {
      cout << "After a replacement: " << 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;       
    int 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;
    }
    else{
        return false;
    }
}

char *search_and_replace_alloc(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 char[size];
    if(pos=strstr(str,oldsubstr)){
         strncpy(result, str, pos-str);
         *(result+(pos-str)) = '\0';
         strcat(result, newsubstr);
         strcat(result, pos+strlen(oldsubstr));
         cout<<
         return result;
    }
    else {
        delete [] 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 (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/

#include
#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 a string class and also "
               "supporting null-terminated strings,\nC++ "
               "offers a rich programming environment for "
               "string-intensive tasks.\nIt's power programming.";
  cout << "Given: " << "\n\n";
  cout << test << endl;
  wc wcd = wordcount(test);
  cout << "\nWords: " << wcd.words << endl;
  cout << "Spaces: " << wcd.spaces << endl;
  cout << "Lines: " << wcd.lines << endl;
  cout << "Punctuation: " << wcd.punct << endl;
  return 0;
}
wc wordcount(const char *str) {
  wc data;  

  if(*str) ++data.lines;
  while(*str) { 

    if(isalpha(*str)) { 
      while(isalpha(*str) || *str == '\'') {
        if(*str == '\'') ++data.punct;
        ++str;
      }
      data.words++; 
    }
    else { 
      if(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
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        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;
  cout << "Obtain the words in a sentence.\n";
  tok = strtok(str, delims);
  while(tok) {
    cout << tok << endl;
    tok  = strtok(NULL, delims);
  }
  char kvpairs[] = "count=10, name=\"Tom Jones, jr.\", max=100, min=0.01";
  char kvdelims[] = " =,";
  cout << "\nTokenize key/Value pairs.\n";
  tok = strtok(kvpairs, kvdelims);
  while(tok) {
    cout << "Key: " << tok << " ";
    if(!strcmp("name", tok)) {
      tok = strtok(NULL, "\"");
    }
    else {
      tok  = strtok(NULL, kvdelims);
    }
    cout << "Value: " << tok << endl;
    tok = strtok(NULL, kvdelims);
  }

  cout <<"Ori String is " << kvpairs  <

  //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);
  }
  cout << "\n\n";
  return 0;
}

const char *gettoken(const char *str) {
  static char token[MAX_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(*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 = '\0';
  return token; 
}

3. String操作实例：

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 (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/

#include
#include
using namespace std;
int main()
{
  // Create some string objects. Three are initialized
  // using the string literal passed as an argument.
  string str1("Alpha");
  string str2("Beta");
  string str3("Gamma");
  string str4;
  // Output a string via cout.
  cout << "Here are the original strings:\n";
  cout << "  str1: " << str1 << endl;
  cout << "  str2: " << str2 << endl;
  cout << "  str3: " << str3 << "\n\n";
  // Display the maximum string length.
  cout << "The maximum string length is: " << str1.max_size()
       << "\n\n";
  // Display the 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
  cout << "str1 contains " << str1.size() << " characters.\n";
  // Display the capacity of str1.
  cout << "Capacity of str1: " << str1.capacity() << "\n\n";
  // Display the characters in a string one at a time
  // by using the indexing operator.
  for(unsigned i = 0; i < str1.size(); ++i)
    cout << "str1["<<<"]: " << str1[i] << endl; //使用at方法也可以
  cout << endl;
  // Assign one string to another.
  str4 = str1; 
  cout << "str4 after being assigned str1: " << str4 << "\n\n";
  // Concatenate two strings.
  str4 = str1 + str3; 
  cout << "str4 after begin assigned st1+str3: " << str4 << "\n\n";
  // Insert one string into another.
  str4.insert(5, str2);
  cout << "str4 after inserting str2: " << str4 << "\n\n";
  // Obtain a substring.
  str4 = str4.substr(5, 4);
  cout << "str4 after being assigned str4.substr(5, 4): " 
       << str4 << "\n\n";
  // Compare two strings.
  cout << "Compare strings.\n";
  if(str3 > str1) cout << "str3 > str1\n"; //使用compare方法能够更加强大的比较String
  if(str3 == str1+str2)
    cout << "str3 == str1+str2\n";
  if(str1 <= str2)
    cout << "str1 <= str2\n\n";
  // Create a string object using another string object.
  cout << "Initialize str5 with the contents of str1.\n";
  string str5(str1);
  cout << "str5: " << str5 << "\n\n";
  // Erase str4.
  cout << "Erasing str4.\n";
  str4.erase(); //使用clear方法也可以
  if(str4.empty()) cout << "str4 is now empty.\n";
  cout << "Size and capacity of str4 is " << str4.size() << " "
       << str4.capacity() << "\n\n";
  // Use push_back() to add characters to str4.
  for(char ch = 'A'; ch <= 'Z'; ++ch)
    str4.push_back(ch);
  cout << "str4 after calls to push_back(): " << str4 << endl;
  cout << "Size and capacity of str4 is now " << str4.size() << " "
       << str4.capacity() << "\n\n";
  // Set the capacity of str4 to 128.
  cout << "Setting the capacity of str4 to 128\n";
  str4.reserve(128);
  cout << "Capacity of str4 is now: " << str4.capacity() << "\n\n";
  // Input a string via cin.
  cout << "Enter a string: ";
  cin >> str1;
  cout << "You entered: " << str1 << "\n\n";
  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 (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/

#include
#include
using namespace std;
void showresult(string s, string::size_type i);
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 a string.
  string str("one two three, one two three");
  string str2;
  cout << "String to be searched: " << str << "\n\n";
  cout << "Searching for the first occurrence of 'two'\n";
  indx = str.find("two");
  showresult(str, indx);
  cout << "Searching for the last occurrence of 'two'\n";
  indx = str.rfind("two");
  showresult(str, indx);
  cout << "Searching for the first occurrence of t or h\n";
  indx = str.find_first_of("th");
  showresult(str, indx);
  cout << "Searching for the last occurrence of t or h\n";
  indx = str.find_last_of("th");
  showresult(str, indx);
  cout << "Searching for the first occurrence of any character other "
       << "than o, n, e, or space\n";
  indx = str.find_first_not_of("one ");
  showresult(str, indx);
  cout << "Searching for the last occurrence of any character other "
       << "than o, n, e or space\n";
  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::npos) { //在没有匹配的部分都是返回npos
    cout << "No match found.\n";
    return;
  }
  cout << "Match found at index " << i << endl;
  cout << "Remaining string from point of match: "
       << s.substr(i) << "\n\n";
}

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
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        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 a test. So is this.";
  cout << "Original string: " << str << "\n\n";
  cout << "Replacing 'is' with 'was':\n";
  // The following replaces is with was. Notice 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");
  cout << "Replace 'So' with 'So too'" << endl;
  search_and_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 (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/
#include
#include
#include
#include
#include
using namespace std;
int main()
{
  string strA("This is a test.");
  // Create an iterator to a string.
  string::iterator itr;
  // Use an iterator to cycle through the characters 
  // of a string.
  cout << "Display a string via an iterator.\n";
  for(itr = strA.begin(); itr != strA.end(); ++itr) 
    cout << *itr;
  cout << "\n\n";
  // Use a reverse iterator to display the string in reverse.
  cout << "Display a string in reverse using a reverse iterator.\n";
  string::reverse_iterator ritr;
  for(ritr = strA.rbegin(); ritr != strA.rend(); ++ritr)
    cout << *ritr;
  cout << "\n\n";
  // Insert into a string via an iterator.
  // First, use the the STL find() algorithm to obtain
  // an iterator to the start of the first 'a'.
  itr = find(strA.begin(), strA.end(), 'a');
  // Next, increment the iterator so that it points to the
  // character after 'a', which in this case is a space.  
  ++itr;
  // Insert into str by using the iterator version of insert(). 
  cout <<"Insert into a string via an iterator.\n";
  string strB(" bigger");
  strA.insert(itr, strB.begin(), strB.end());
  cout << strA << "\n\n";
  // Now, replace 'bigger' with 'larger'.
  cout << "Replace bigger with larger.\n";
  itr = find(strA.begin(), strA.end(), 'b');
  strA.replace(itr, itr+6, "larger");
  cout << strA << "\n\n";
  // Now, remove ' larger'.
  cout << "Remove ' larger'.\n";
  itr = find(strA.begin(), strA.end(), 'l');
  strA.erase(itr, itr+7);
  cout << strA << "\n\n";
  // Use an iterator with the STL transform() algorithm to convert
  // a string to uppercase.
  cout << "Use the STL transform() algorithm to convert a "
       << "string into uppercase.\n";      
  transform(strA.begin(), strA.end(), strA.begin(), toupper);
  cout << strA << "\n\n";
  // Create a string from a vector.
  vector vec;
  for(int i=0; i < 10; ++i)
    vec.push_back('A'+i);
  string strC(vec.begin(), vec.end());
  cout << "Here is strC, which is constructed from a vector:\n";
  cout << strC << endl;
  return 0;
}

Ex12忽略大小写的搜索替换

/*
* =====================================================================================
*
*       Filename:  2-14.cpp
*
*    Description:  Search and Replace a substring ignoring the case
*
*        Version:  1.0
*        Created:  05/14/2010 07:10:20 PM
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/

#include
#include
#include
#include
using namespace std;
bool comp_ign_case(char x, char y);
string::iterator search_ign_case(string &str, const string &substr);
bool search_and_replace_ign_case(string &str, const string &oldsubstr,
                                 const string &newsubstr);
int main()
{
  string strA("This is a test of case-insensitive searching.");
  string strB("test");
  string strC("TEST");
  string strD("testing");
  cout << "First, demonstrate search_ign_case().\n";
  cout << "String to be searched:\n" << strA << "\n\n";
  cout << "Searching for " << strB << ". ";
  if(search_ign_case(strA, strB) != strA.end())
    cout << "Found!\n";
  cout << "Searching for " << strC << ". ";
  if(search_ign_case(strA, strC) != strA.end())
    cout << "Found!\n";
  cout << "Searching for " << strD << ". ";
  if(search_ign_case(strA, strD) != strA.end())
    cout << "Found!\n";
  else
    cout << "Not Found.\n";
  // Use the iterator returned by search_ign_case() to display
  // the remainder of the string.
  cout << "\nRemainder of string after finding 'of':\n";
  string::iterator itr = search_ign_case(strA, "of");
  while(itr != strA.end()) 
    cout << *itr++;
  cout << "\n\n";
  // Now, demonstrate search and replace.
  strA = "Alpha Beta Gamma alpha beta gamma";
  cout << "Now demonstrate search_and_replace_ign_case().\n";
  cout << "String that will receive replacments:\n" << strA << "\n\n";
  cout << "Replacing all occurrences of alpha with zeta:\n";
  while(search_and_replace_ign_case(strA, "alpha", "zeta"))
    cout << strA << endl;
  return 0;
}
string::iterator search_ign_case(string &str, const string &substr) {
  return search(str.begin(), str.end(),
                substr.begin(), substr.end(),
                comp_ign_case);
}  
bool comp_ign_case(char x, char y) {
  return tolower(x) == tolower(y);
}
bool search_and_replace_ign_case(string &str, const string &oldsubstr,
                        const string &newsubstr) {
  string::iterator startitr;
  startitr = search_ign_case(str, oldsubstr);
  if(startitr != str.end()) {
    str.replace(startitr, startitr+oldsubstr.size(), newsubstr);
    return true;
  }
  return false;
}

Ex13String转化为普通字符串

/*
* =====================================================================================
*
*       Filename:  2-15.cpp
*
*    Description:  Convert String to the C type string using c_str
*
*        Version:  1.0
*        Created:  05/16/2010 03:10:12 PM
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/
#include
#include
#include
using namespace std;
int main()
{
  string str("This is a test.");
  char cstr[80];
  cout << "Here is the original string:\n";
  cout << str << "\n\n";
  // Obtain a pointer to the string.
  const char *p = str.c_str();
  cout << "Here is the null-terminated version of the string:\n";
  cout << p << "\n\n";
  // Copy the string into a statically allocated array.
  //
  // First, confirm that the array is long enough
  // to hold the string.
  if(sizeof(cstr) < str.size() + 1) {
    cout << "Array is too small to hold the string.\n";
    return 0;
  }
  strcpy(cstr, p); //因为返回的是const类型， 通常我们需要将这个字符串拷贝出来
  cout << "Here is the string copied into cstr:\n" << cstr << "\n\n";
  // Next,copy the string into a dynamically allocated array.
  try {
    // Dynamically allocate the array.
    char *p2 = new char[str.size()+1];
    // Copy the string into the array.
    strcpy(p2, str.c_str());
    cout << "String after being copied into dynamic-allocated array:\n";
    cout << p2 << endl;
    delete [] p2;
  } catch(bad_alloc ba) {
    cout << "Allocation Failure\n";
    return 1;
  }
  return 0;
}

Ex14为String重载减法运算

/*
* =====================================================================================
*
*       Filename:  2-16.cpp
*
*    Description:  Override the - and -= operation in String
*
*        Version:  1.0
*        Created:  05/16/2010 03:38:14 PM
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  gnuhpc (http://blog.csdn.net/gnuhpc) , warmbupt@gmail.com
*        Company:  IBM CDL
*
* =====================================================================================
*/

#include
#include
using namespace std;
string operator-(const string &left, const string &right);
string operator-=(string &left, const string &right);
int main()
{
  string str("This is a test.");
  string res_str;
  cout << "Contents of str: " << str << "\n\n";
  // Subtract "is" from str and put the result in res_str.  
  res_str =  str - "is";
  cout << "Result of str - \"is\": " << res_str << "\n\n";
  // Use -= to subract "is" from res_str. This puts the result
  // back into res_str.
  res_str -= "is";
  cout << "Result of res_str -= \"is\": " << res_str << "\n\n";
  return 0;
}
string operator-(const string &left, const string &right) {
  string::size_type i;
  string result(left);
  i = result.find(right);
  if(i != string::npos) 
    result.erase(i, right.size());
  return result;
}
string operator-=(string &left, const string &right) {
  string::size_type i;
  i = left.find(right);
  if(i != string::npos) 
    left.erase(i, right.size());
  return left;
}