STL notes (IV): String

STL note （ Four ）： character string

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

// www.cplusplus.com -  documentation 

//  Creation and initialization of strings 
void test1()
{
    string s1;
    string s2("Reyn");
    string s3(s2); //  Copy structure 
    string s4(s2, 0, 2); //  Start from zero , Length is two 
    string s5 = "Lisa"; //  assignment - Operator overloading 
    string s6 = s2 + "Good!"; //  Sum up - Operator overloading  -  String splicing 
    string s7(s2.begin(), s2.end() + 1); // s6 = s2 [ ) -  Left closed right away 
    string s8(s2.begin(), s2.begin() + 3); // "Rey"
}

//  String basic operation 
void test2()
{
    // 1.  Reading data 
    string s = "How are you";
    cout << s[0] << endl;    // 'H', Do not detect out of bounds 
    cout << s.at(0) << endl; // 'H', Exceptions will be thrown for out of bounds operations 

    // 2.  length 
    cout << s.size() << endl;

    // 3.  Substring 
    cout << s.substr(0, 7) << endl;

    // 4.  Replace 
    cout << s.replace(0, 1, "h") << endl;

    // 5.  In exchange for 
    string str1 = "Reyn";
    string str2 = "Lisa";
    str1.swap(str2);
    cout << str1 << ' ' << str2 << endl;

    // 6.  Compare 
    if (str1 > str2)
        cout << "fuc" << endl;
    if (str1 == str2)
        cout << "Nice job" << endl;
}

//  Insert 、 Delete 
void test3()
{
    // 1.  Insert 
    string s = " do ";
    s.insert(0, "How"); //  Insert at any position 
    s.append("you do"); //  Append the string to the end 
    s += "?";           //  String splicing 
    cout << s << endl;  // How do you do?

    // 2.  Delete 
    s.erase(0, 4);
    s.erase(6);
    s.erase(s.begin(), s.begin() + 3);
    s.erase(s.begin());
    cout << s << endl;
}

//  Inquire about 
void test4()
{
    string s = "How are you?";
    int position;
    position = s.find("are");
    position = s.find("fuck"); //  Returns... When there is no string in the string  -1
    position = s.find("o", 5);
    cout << position << endl;

    //  The first character position that matches any character in the specified string 
    position = s.find_first_of("oau");
    cout << position << endl;
    //  The last character position that matches any character in the specified string 
    position = s.find_last_of("oau");
    cout << position << endl;
    //  The first character position that does not match all characters in the specified string 
    position = s.find_first_not_of("oau");
    cout << position << endl;
    //  The last character position that does not match all characters in the specified string 
    position = s.find_last_not_of("oau");
    cout << position << endl;
}

//  Conversion between integer and string 
void test5()
{
    //  Integer to string  ------- 45 -- Out --> str( Character stream - Memory ,text) -- Enter into --> s
    int num = 45;
    string s;
    stringstream str;
    str << num;
    str >> s;
    cout << s << endl;

    str.clear(); //  Empty the string buffer , You can also redeclare a character stream 

    //  String to integer  ------- t -- Out --> str( Character stream ) -- Enter into --> mun
    string t = "56";
    int mun;
    str << t;
    str >> mun;
    cout << mun << endl;
}

//  Split string  ------- str( Memory ) -- Enter into --> s
void test6()
{
    string str = "how are you";
    string s;

    istringstream in(str);

    while (!in.eof()) { //  Execute a loop when the string stream does not reach the end 
        in >> s;
        cout << s << endl;
    }

    cout << endl;
    //  The separator is a comma 
    string rts = "how,are,you";
    istringstream ni(rts);
    while (!ni.eof()) {
        getline(ni, s, ','); //  Use comma as separator , Stream characters (ni) The substring in is assigned to the string variable (s)
        cout << s << endl;
    }

}

//  Remove spaces at both ends of the string 
void test7()
{
    string s = "  Hello World  ";
    cout << s << endl;

    s.erase(0, s.find_first_not_of(' '));
    s.erase(s.find_last_not_of(' ') + 1);
    cout << s << endl;
}

int main()
{
    // test1(); //  Creation and initialization of strings 
    // test2(); //  String basic operation 
    // test3(); //  Insert 、 Delete 
    // test4(); //  Inquire about 
    // test5(); //  Conversion between integer and string 
    // test6(); //  Split string 
    // test7(); //  Remove spaces at both ends of the string 
    return 0;
}

Created on initialization

• Default structure
• Copy structure
• Operator overloading
• iterator

Basic operation

• Reading data ：s[0]; s.at();
• length ：s.size();
• Substring ：s.substr();
• Replace ：s.replace();
• In exchange for ：s.swap();
• Compare ：< <= > >= == !=

Insert 、 Delete 、 Inquire about

• Insert ：s.insert();
• Delete ：s.erase();
• Inquire about ：s.find();

flow

The various streams in the standard template library can be regarded as the channels of data from one data store to another （ medium ）, One of the buffers is usually a program . therefore , It can be constructed by “ flow ” Object to establish the channel between the program and other storage areas , Through the unique characteristics of each flow , It can simply complete some functions .

In the next article , We will introduce C++ Iterators in