C++/Data Type/String

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Accessing Characters In Strings

 
#include <iostream>
#include <string>
#include <cctype>
using namespace std;
int main()
{
   string text;                  
          
   cout << "Counts words. Enter a text and terminate with a period and return:\n";
   
   getline( cin, text, ".");     // Reads a text up to the first "."
   int  i,                             // Index
        numberOfWhiteSpace = 0,        // Number of white spaces
        numberOfWords  = 0;            // Number of words
   bool fSpace = true;                 // Flag for white space
   for( i = 0; i < text.length(); ++i)
   {
      if( isspace( text[i]) )          // white space?
      {
         ++numberOfWhiteSpace;  
         fSpace = true;
      }
      else if( fSpace)                 // At the beginning of a word?
      {
         ++numberOfWords;   
         fSpace = false;
      }
   }
   cout << "\nYour text contains (without periods)"
        << "\ncharacters: " << text.length()
        << "\nwords: " << numberOfWords
        << "\nwhite spaces: " << numberOfWhiteSpace
        << endl;
   return 0;
}


Adding Strings

 
#include <iostream>
#include <string>
using namespace std;
int main(void)
{
   string firstName = "gggg";
   string lastName = "uuuut";
   cout << "Your name is " << firstName + lastName;
   return 0;
}


A filter to remove white-space characters at the ends of lines.

 
#include <iostream>
#include <string>
using namespace std;
void cutline( void );         
string line;                  
int main()
{
   while( getline(cin, line)) {
     cutline();               
     cout << line << endl;    
   }
   return 0;
} 
void cutline()
{
   int i = line.size();       
                              
   while( i-- >= 0 )
     if(   line[i] != " " && line[i] != "\t" )
       break;                   
   line.resize(++i);            
}


A short string demonstration

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
  string stringObject1("stringObject1");
  string stringObject2("stringObject2");
  string stringObject3("stringObject3");
  string stringObject4;
  stringObject4 = stringObject1;
  cout << stringObject1 << "\n" << stringObject3 << "\n";
  stringObject4 = stringObject1 + stringObject2;
  cout << stringObject4 << "\n";
  stringObject4 = stringObject1 + " to " + stringObject3;
  cout << stringObject4 << "\n";
  if(stringObject3 > stringObject1) 
     cout << "stringObject3 > stringObject1\n";
  if(stringObject3 == stringObject1+stringObject2)
    cout << "stringObject3 == stringObject1+stringObject2\n";
  stringObject1 = "This is a null-terminated string.\n";
  cout << stringObject1;
  string str5(stringObject1);
  cout << str5;
  cout << "Enter a string: ";
  cin >> str5;
  cout << str5;
  return 0;
}


A string demonstration: assignment, concatenate, compare

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
  string str1("Alpha");
  string str2("Beta");
  string str3("Omega");
  string str4;
  str4 = str1; 
  cout << str1 << endl << str3 << endl;
  
  str4 = str1 + str2;            // concatenate two strings
  cout << str4 << endl;
  str4 = str1 + " to " + str3;
  cout << str4 << endl;
  
  if(str3 > str1)                // compare strings
     cout << "str3 > str1\n";
  if(str3 == str1 + str2)
    cout << "str3 == str1+str2\n";
  str1 = "This is a null-terminated string.\n";
  cout << str1;
  // create a string object using another string object
  string str5(str1);
  cout << str5;
  // input a string
  cout << "Enter a string: ";
  cin >> str5;
  cout << str5;
  return 0;
}


Demonstrate insert(), erase(), and replace().

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
  string str1("www.java2s.com");
  string str2("STL Power");
  cout << "Initial strings:\n";
  cout << "str1: " << str1 << endl;
  cout << "str2: " << str2 << "\n\n";
  // insert()
  cout << "Insert str2 into str1:\n";
  str1.insert(6, str2);
  cout << str1 << "\n\n";
  // erase()
  cout << "Remove 9 characters from str1:\n";
  str1.erase(6, 9);
  cout << str1 <<"\n\n";
  // replace 
  cout << "Replace 8 characters in str1 with str2:\n";
  str1.replace(7, 8, str2);
  cout << str1 << endl;
  return 0;
}


Inputting Multiple Words into a String

 
#include <iostream>
using namespace std;
#include <string>
int main(void)
{
   string name;
   cout << "Enter your name: ";
   cin >> name;
   cout << "Your name is " << name;
   return 0;
}


Insert, search, and replace in strings.

 
#include <iostream>
#include <string>
using namespace std;
string stringObject1 = "As 111 555 ...",
              stringObject2 = "number ";
int main()
{
   int pos = 0;
   cout << "stringObject1 : " << stringObject1 << endl;
   cout << "\nInserting in string: " << stringObject2 <<""<< endl;
   pos = stringObject1.find("555");
   if( pos != string::npos )
      stringObject1.insert(pos,stringObject2);
   cout << "stringObject1 : " << stringObject1 << endl;             
   cout << "\nTo erase remaining characters behind 555:"
        << endl;
   pos = stringObject1.find("555");
   if( pos != string::npos )
      stringObject1.erase(pos + 3);
   cout << "stringObject1 : " << stringObject1 << endl;             
   cout << "\nTo replace 111 by 222:"
        << endl;
   pos = stringObject1.find("111");
   if( pos != string::npos )
      stringObject1.replace(pos, 4, "222");
   cout << "stringObject1 : " << stringObject1 << endl;             
   return 0;
}


Print a name in two different formats

 
#include <iostream>
#include <string>
using namespace std;
const string FIRST = "First";    
const string LAST = "Last";      
const char MIDDLE =   "M";        
int main()
{
    string firstLast;   
    string lastFirst;   
    firstLast = FIRST + " " + LAST;
    cout << "Name in first-last format is " << firstLast << endl;
    lastFirst = LAST + ", " + FIRST + ", ";
    cout << "Name in last-first-initial format is ";
    cout << lastFirst << MIDDLE << "." << endl;
    return 0;
}


Read string from console

 
#include <iostream>
using namespace std;
int main(void)
{
   int myWeight, myHeight;
   string myName;
   cout << "Enter your name: ";
   cin >> myName;
   cout << "Enter your weight in pounds: ";
   cin >> myWeight;
   cout << "Enter your height in inches: ";
   cin >> myHeight;
   cout << "Your name score is " << myName << "\n";
   cout << "Your weight in pounds is " << myWeight << "\n";
   cout << "Your height in inches is " << myHeight << "\n";
   return 0;
}


Several string operations: substr

 
#include <iostream>
#include <string>   
using namespace std;
int main()
{
    string fullName;
    string name;
    string::size_type startPos;
    fullName = "Full name";
    startPos = fullName.find("name");
    name = "Mr. " + fullName.substr(startPos, 8);
    cout << name << endl;
    return 0;
}


String Char Indexing

 
#include <string>
#include <iostream>
using namespace std;
int main()
{
    string str( "hello" );
    char ch = str[0];                       
    str[0] = "j";                           
    ch = str. at( 0 );                      
    str.at(0) = "h";                        
    ch = str[ 1000 ];                       
    return 0  ; 
}


String Find and replace

 
#include <string> 
#include <iostream>
using namespace std;
int main()
{
    string str( "a bc abc abcd abcde" );
    string searchString( "hello" ); 
    string replaceString( "ab" );
    assert( searchString != replaceString );
    string::size_type pos = 0;
    while ( (pos = str.find(searchString, pos)) != string::npos ) {
        str.replace( pos, searchString.size(), replaceString );
        pos++;
    }
    cout << str << endl;
    return 0;
}


string: find( ) and rfind( )

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
  int i;
  string stringObject1 = "Quick of Mind, Strong of Body, Pure of Heart";
  string stringObject2;
  i = stringObject1.find("Quick");
  if(i!=string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    stringObject2.assign(stringObject1, i, stringObject1.size());
    cout << stringObject2;
  }
  cout << "\n\n";
  i = stringObject1.find("Strong");
  if(i!=string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    stringObject2.assign(stringObject1, i, stringObject1.size());
    cout << stringObject2;
  }
  cout << "\n\n";
  i = stringObject1.find("Pure");
  if(i!=string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    stringObject2.assign(stringObject1, i, stringObject1.size());
    cout << stringObject2;
  }
  cout << "\n\n";
  // find list "of"
  i = stringObject1.rfind("of");
  if(i!=string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    stringObject2.assign(stringObject1, i, stringObject1.size());
    cout << stringObject2;
  }
  return 0;
}


String insert(), erase(), and replace()

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
  string stringObject1("stringObject1");
  string stringObject2("stringObject2");
  cout << "Initial strings:\n";
  cout << "stringObject1: " << stringObject1 << endl;
  cout << "stringObject2: " << stringObject2 << "\n\n";
  cout << "Insert stringObject2 into stringObject1:\n";
  stringObject1.insert(6, stringObject2);
  cout << stringObject1 << "\n\n";
  cout << "Remove 9 characters from stringObject1:\n";
  stringObject1.erase(6, 9);
  cout << stringObject1 <<"\n\n";
  cout << "Replace 8 characters in stringObject1 with stringObject2:\n";
  stringObject1.replace(7, 8, stringObject2);
  cout << stringObject1 << endl;
  return 0;
}


String Size

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
    string str = "0123456789";
    cout << "The current capacity of the string is:" << str.size() << endl;
    str.resize( 20 );
    cout << "The new capacity of the string is:"
         << str.size() << endl;           
    cout << "The actual length of the string is: "
         << strlen( str.c_str() ) << endl;
    cout << "The string object after resizing "
         << "to 20 a 10 character string: "
         << str << endl;
    str += "hello";
    cout << str << endl;
    return 0;
}


String SizeOf

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
  cout << sizeof( "hello" ) << endl;       
  cout << sizeof( "hello there" ) << endl; 
  string stringObject1 = "hello";
  string stringObject2 = "hello there";
  cout << sizeof( stringObject1 ) << endl;          
  cout << sizeof( stringObject2 ) << endl;          
  char* s1 = "hello";
  char* s2 = "hello there";
  cout << sizeof( s1 ) << endl;   
  cout << sizeof( s2 ) << endl;   
  char c_arr[] = "how are you?";
  cout << sizeof( c_arr ) << endl;
  return 0;
}


Strings: size, iterator, count, begin and end

 
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main()
{
  string str1("www.java2s.com");
  string::iterator p;
  unsigned int i;
  // use size()
  for(i = 0; i <str1.size(); i++)
    cout << str1[i];
  cout << endl;
  // use iterator
  p = str1.begin();
  while(p != str1.end()) 
    cout << *p++;
  cout << endl;
  // use the count() algorithm
  i = count(str1.begin(), str1.end(), "i");
  cout << "There are " << i << " i"s in str1\n";
  p = str1.begin();
  while(p != str1.end()) 
    cout << *p++;
  cout << endl;

  return 0;
}


String type class

 
#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
class StringClass {
  char *p;
  int len;
public:
  StringClass(char *ptr)
  {
    len = strlen(ptr);
    p = (char *) malloc(len+1);
    if(!p) {
      cout << "Allocation error\n";
      exit(1);
    }
    strcpy(p, ptr);
  }
  ~StringClass() { 
    cout << "Freeing p\n"; free(p); 
  }
  void show() 
  {
    cout << p << " - length: " << len;
    cout << endl;
  }
};
int main()
{
  StringClass stringObject1("www.java2s.com"), stringObject2("www.java2s.com");
  stringObject1.show();
  stringObject2.show();
  return 0;
}


string variable instead of a character array

 
#include <iostream>
using namespace std;
#include <string>
int main(void)
{
   string name;
   cout << "Enter your name: ";
   cin >> name;
   cout << "Your name is " << name;
   return 0;
}


Use string: find, string::npos

 
#include <iostream>
#include <string>
using namespace std;
int main()
{
  int i;
  string s1 = "Quick of Mind, Strong of Body, Pure of Heart";
  string s2;
  i = s1.find("Quick");
  if(i != string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    s2.assign(s1, i, s1.size());
    cout << s2;
  }
  cout << endl;
  i = s1.find("Strong");
  if(i != string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    s2.assign(s1, i, s1.size());
    cout << s2;
  }
  cout << endl;
  i = s1.find("Pure");
  if(i!=string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    s2.assign(s1, i, s1.size());
    cout << s2;
  }
  cout << endl;
  // find list "of"
  i = s1.rfind("of");
  if(i!=string::npos) {
    cout << "Match found at " << i << endl;
    cout << "Remaining string is:\n";
    s2.assign(s1, i, s1.size());
    cout << s2;
  }
  return 0;
}
Источник — «http://cppe.ru/index.php?title=C%2B%2B/Data_Type/String&oldid=1599»