string type of C ++ Standard Library

stirng type

Summary:

Types of C ++ Standard Library: string
variable-length string of
simple operation
 only comprises personal common function

head File

As with other types of string library types, corresponding to the need to include header files

#include<string>
using namespace std;

define and initialize the string type

Definition and initialization	Explanation
string s1 = "C++";	Create a string s1, if omitted = "C ++" null string
stirng s2(s1);	Create and initialize a string value s1 s2 value ( C ++ )
string s3("Love")	String s3 created and initialized to Love
string s4(6,'I')	S4 and create a string initialized to 6 consecutive characters 'I', a string consisting of

string type of function

• Assignment of strings

  string s1 = "I LOVE C++";
  string s2;
  s2 = s1;
  cout<<s2;

  Input and output:

  I LOVE C++

• String + operator + =

  string s1 = "I ";
  string s2 = "LOVE ";
  string s3 = "C++";
  s1 = s1 + s2;
  cout<<s1<<endl;
  s1 += s3;
  cout<<s1<<endl;

  Input and output:

  I LOVE
  I LOVE C++

• String relational operators

  string type can be used directly ==,! =,>, <,> =, <=, etc. relational operators to compare strings, and returns a Boolean type

  //EG:
  string s1 = "123";
  string s2 = "123";
  cout<<(s1 == s2 ? "s1 = s2" : "s1 != s2");

  Input and output:

  s1 = s2

• Read a string

  1. cin way

     Whitespace characters automatically ignored when reading the beginning of
     the character when reading the event of a blank character, the end of the reading

     string s1;  
     cin>>s1;  
     cout<<s1;  

     Input and output:

     Hello World
     Hello

  2. getline way

     Included in the string library

     1. istream& getline (istream& is, string& str);

        string str;
        getline(cin,str);
        cout<<str;

        Input and output:

        Hello World
        abc
        Hello World

        Each entry is a single line encounters '\ n' input end

     2. istream& getline (istream& is, string& str, char delim);

        string str;
        getline(cin,str,'#');
        cout<<str;

        Input and output:

        abc def#abc
        abc def

        When a '#' character to the end of the operation, '#' and '#' character is not read after

• String length

  size () / lenth () can return the string length (byte length)

  string s1;
  cout<<s1.size()<<endl;
  cout<<s1.lenth()<<endl;
  
  s1 = "Hello World";
  cout<<s1.size()<<endl;
  cout<<s1.lenth()<<endl;
  
  s1 = "你好";
  cout<<s1.size()<<endl;
  cout<<s1.lenth()<<endl;

  Input and output:

  0
  0
  11
  11
  4
  4

• Get the character string

  str [n]: Returns the n-th str characters from 0 to size () - 1

  string str = "I Love C++"
  cout<<str[0]<<endl;
  a[7] = 'A';
  cout<<str;

  Input and output:

  I
  I Love A++

• Sentenced empty string

  empty () returns a Boolean type

  string s1;
  if(s1.empty())
      cout<<"s1字符串为空";

  Input and output:

  s1 string is empty

• String search

  string in the find () return value is the first character or string that appears in the index, if not found, it will return npos.

  string s1 = "C++";
  string s2 = "I LOVE C++";
  cout<<s1.find(s2)<<endl;
  cout<<s1.find("Hello")<<endl;

  Input and output:

  . 7
  4,294,967,295 (maximum value or minimum value)

• Ordering within the string

  string str = "cba";
  sort(str.begin(), str.end());
  cout<<str;

  Input and output:

  abc