STL::string类

本文摘自《21天学通C++》
最常用的字符串函数包括：

• 复制
• 连接
• 查找字符和字符串
• 截断
• 使用标准模版库提供的算法实现字符串反转和大小写转换
  使用STL string类，需包含头文件
  1、实例化STL string及复制

#include "stdafx.h"#include <string>#include <iostream>using namespace std;int main(){    // 初始化一个常量字符串并将其赋值给一个STL string对象    const char* pszConstString = "Hello String!";    cout << "Constant string is:" << pszConstString << endl;    std::string strFromConst(pszConstString);    cout << "strFromConst is:" << strFromConst << endl;    std::string str2("Hello String!");    std::string str2Copy(str2);//用一个string对象来初始化另一个    cout << "str2Copy is:" << str2Copy << endl;    //Initialize a string to the first 5 characters of another    std::string strPartialCopy(pszConstString, 5);    //让string的构造函数只接受输入字符串的前n个字符    cout << "strPartialCopy is:" << strPartialCopy << endl;    //Initialize a string object to contain 10 'a's    //初始化string对象，使其包含指定数量的特定字符    std::string strRepeatChars(10, 'a');    cout << "strRepeatChars is:" << strRepeatChars << endl;    return 0;}

2、访问string及其内容
访问STL string的字符内容，可使用迭代器，也可采用类似于数组的语法并使用下标运算符（【】）提供偏移量；要获得string对象的C风格表示，可使用成员函数c_str()，

#include "stdafx.h"#include <string>#include <iostream>using namespace std;int main(){    string strSTLString("Hello String");    cout << "Diaplaying characters using array-syntax:" << endl;    for (size_t nCharCounter = 0; nCharCounter < strSTLString.length(); ++nCharCounter)    {        cout << "Character[" << nCharCounter << "] is:";        cout << strSTLString[nCharCounter] << endl;    }    cout << endl;    //Access the contants of a string using iterators    cout << "Diapalying characters using iterators:" << endl;    int nCharOffset = 0;    string::const_iterator iCharacterLocator;    for (iCharacterLocator = strSTLString.begin(); iCharacterLocator != strSTLString.end(); ++iCharacterLocator)    {        cout << "Character[" << nCharOffset++ << "] is:";        cout << *iCharacterLocator << endl;    }    cout << endl;    //Access the contents of a string as a C-style string    cout << "The char* representation of the string is:";    cout << strSTLString.c_str() << endl;    getchar();    return 0;}

3、字符串连接
要连接字符串，可以使用运算符+=，也可使用成员函数append

#include "stdafx.h"#include <string>#include <iostream>using namespace std;int main(){    string strSample1("Hello");    string strSample2("String!");    //Concatenate    strSample1 += strSample2;    cout << strSample1 << endl << endl;    string strSample3("Fun is not needing to use pointers!");    strSample1.append(strSample3);    cout << strSample1 << endl << endl;    const char* pszConstString = "You however still can!";    strSample1.append(pszConstString);    cout << strSample1 << endl;    getchar();    return 0;}

4、在string中查找字符或字符串
STL string类提供了成员函数find，该函数有多个重载版本，可在指定string对象中查找字符或字符串，

#include "stdafx.h"#include <string>#include <iostream>using namespace std;int main(){    string strSample("Good day String! Today is beautiful!");    cout << "The sample string is:" << endl;    cout << strSample << endl << endl;    //Find substring "day" in it    size_t nOffset = strSample.find("day", 0);    //Check if the substring was found    if (nOffset != string::npos)        cout << "First instance of\"day\" was found at offset" << nOffset;    else        cout << "Substring not found." << endl;    cout << endl << endl;    cout << "Locating all instance of substring \"day\"" << endl;    size_t nSubstringOffset = strSample.find("day", 0);    while (nSubstringOffset != string::npos)    {        cout << "\"day\"found at offset" << nSubstringOffset << endl;        //Make the 'find' function search the next character onwards        size_t nSearchOffset = nSubstringOffset + 1;        nSubstringOffset = strSample.find("day", nSearchOffset);    }    cout << endl;    cout << "Locating all instance of character 'a'" << endl;    const char chCharToSearch = 'a';    size_t nCharacterOffset = strSample.find(chCharToSearch, 0);    while (nCharacterOffset != string::npos)    {        cout << "'" << chCharToSearch << "' found";        cout << " at position: " << nCharacterOffset << endl;        //Make the 'find' function search forward from the next character onwards        size_t nCharSearchOffset = nCharacterOffset + 1;        nCharacterOffset = strSample.find(chCharToSearch, nCharSearchOffset);    }    getchar();    return 0;}

5、截短STL string
STL string类提供了erase函数，可用于：

• 在给定偏移量和字符数时删除指定数目的字符；
• 在给定指向字符的迭代器时删除字符；
• 在给定由两个迭代器指定的范围时删除该范围内的字符。

#include "stdafx.h"#include <string>#include <iostream>using namespace std;#include <algorithm>int main(){    string strSample("Hello String! Wake up to a beautiful day!");    cout << "The original sample string is: " << endl;    cout << strSample << endl << endl;    //Delete characters from the string given position and count    cout << "Truncating the second sentence: " << endl;    strSample.erase(13, 28);//从第13个字符后删除28个字符    cout << strSample << endl << endl;    //Find a character 'S' in the string using STL find algorithm    string::iterator iCharS = find(strSample.begin(), strSample.end(), 'S');    //If character found ,'erase' to deletes a character    cout << "Erasing character 'S' from the sample string:" << endl;    if (iCharS != strSample.end())        strSample.erase(iCharS);    cout << strSample << endl << endl;    //Erase a range of characters using an overloaded version of erase()    cout << "Erasing a range between begin() and end():" << endl;    strSample.erase(strSample.begin(), strSample.end());    //Verify the length after the erase() operation above    if (strSample.length() == 0)        cout << "The string is empty" << endl;    getchar();    return 0;}

6、字符串反转
需要包含头文件
#include <algorithm>
判读输入的字符串是否是回文：
std::string

#include "stdafx.h"#include <string>#include <iostream>using namespace std;#include <algorithm>int main(){    string strSample("Hello String! We will reverse you!");    cout << "The original sample string is: " << endl;    cout << strSample << endl << endl;    reverse(strSample.begin(), strSample.end());    cout << "After applying the std::reverse algorithm: " << endl;    cout << strSample;    getchar();    return 0;}

7、字符串的大小写转换
std::transform,

#include "stdafx.h"#include <string>#include <iostream>#include <algorithm>using namespace std;int main(){    cout << "Please enter a string for case-conversion:" << endl;    cout << "> ";    string strInput;    getline(cin, strInput);    cout << endl;    transform(strInput.begin(), strInput.end(), strInput.begin(), toupper);    cout << "The string converted to upper case is: " << endl;    cout << strInput << endl << endl;    transform(strInput.begin(), strInput.end(), strInput.begin(), tolower);    cout << "The string converted to lower case is: " << endl;    cout << strInput << endl << endl;    getchar();    return 0;

7、基于模版STL string实现