Brush all kinds of problems encountered string

 

A, C ++ strcpy string assignment function

strcpy(Cstring, value);

Cstring received value is the name of the variable, and the value is the name of a string constant, or another string variable C

#include <iostream>
#include<string.h>
using namespace std;

int main()
{
    const int SIZE = 12;
    char name1[SIZE], name2[SIZE];
    strcpy(name1, "Sebastian");
    cout << "name1：" << name1 << endl;
    strcpy(name2, name1);    //将  name1 赋值给 name2 
    cout << "name2：" << name2 << endl;
    return 0;
}

 

 

Two, C ++ Other common string handling functions:

 

 

• 1. append () - Add character at the end of the string
• 2. find () - Find a string in a string
• 4. insert () - Insert character
• 5. length () - returns a string length
• 6. replace () - replacement string
• 7. substr () - returns a substring

Example:

#include <the iostream> 
#include < string >
 the using  namespace STD; 

int main () 
{ 
    // definition of a string class object 
    string HTTP = " www.runoob.com " ; 

   // print string length 
   cout << http.length ( ) << endl; 

    // stitching 
    http.append ( " / C ++ " ); 
    cout << endl << HTTP; // print results: www.runoob.com/C++ 

    // delete 
    int POS = http.find ( " / C ++ " ); // Find"C ++ "position in the string
    POS << << cout endl; 
    http.replace (POS, 4 , "" );    // starting at position pos, 4 characters after replacement is empty, ie delete 
    cout << HTTP << endl; 

    // find child string runoob 
    int First http.find_first_of = ( " . " ); // '.' character position from the beginning to find 
    int Last http.find_last_of = ( " . " );    // '.' character from the beginning to find the position of the tail 
    cout http.substr << (First + . 1 , Last-First- . 1 ) << endl; // extract "runoob" substring and print 

    return  0 ;
}

 

 

 

Three, stringstream common usage presentation

<Sstream> defines three classes: istringstream, ostringstream and the stringstream, it is used for the input stream, input and output operations and output

<sstream> primarily for data type conversion , since <sstream> using an array instead of the character string object (the snprintf mode), to avoid the risk of buffer overflow ; Also, since the type of the target object and passed parameters are automatically derived out so wrong character formatting problem does not exist. Simply put, compared with the data type conversion c library, <sstream> more secure, automatic and direct

(1) Data type conversion

#include < String > 

#include <sstream> 

#include <the iostream> 

#include <stdio.h> the using namespace STD; int main () 
{ 
    the stringstream sstream; String strResult; int nValue is = 1000 ; // will put an int the input stream 
    sstream << nValue is; // extract a value of type int inserted before sstream from, the assigned string type 
    sstream >> strResult; 
    COUT << " [COUT] strResult iS: " << strResult << endl;
    printf(

 

 

 





    

    

 

    


    


 

"[printf]strResult is: %s\n", strResult.c_str());

 

    return 0;

}

 

 

(2) stitching a plurality of strings

Stringstream stored in the plurality of strings, to achieve the purpose of splicing a plurality of strings (in fact, can be implemented using the string class), while the method described emptying of stringstream

#include <string>
#include <sstream>
#include <iostream>
using namespace std;
int main()
{
    stringstream sstream;
    // 将多个字符串放入 sstream 中
    sstream << "first" << " " << "string,";
    sstream << " second string";
    cout << "strResult is: " << sstream.str() << endl;

    Clear sstream//
    sstream.str("");
    sstream << "third string";
    cout << "After clear, strResult is: " << sstream.str() << endl;
    return 0;

}

 

1.  May be used str () method to convert a string type stringstream type ;
2.  A plurality of strings can be placed in stringstream, Mosaic of the destination string;
3.  If you want to clear stringstream, you must use sstream.str ( ""); fashion;
4. clear () method is suitable for multiple scene data type conversion, see the examples of the link

Details can poke link above

 

 

四、C++ isalpha、isalnum、islower、isupper

These functions are <the cctype> (i.e., C language <ctype.h> header file) inside

 

 

 

In general:

• the isalpha (letters, uppercase, lowercase)
• islower (lowercase)
• isupper (capital letters)
• isalnum (capital letters + numbers lowercase)
• ISBLANK (Space and \ t)
• isspace（space、\t、\r、\n）