从零开始学C++之标准库类型（一）：string 类简介和例程

来源：互联网发布：大数据下的市场营销编辑：程序博客网时间：2024/06/15 09:54

一、标准库string类型
string类型支持长度可变的字符串，C++标准库将负责管理与存储字符相关的内存，以及提供各种有用的操作，在VC中直接F1查看

template <   class CharType,   class Traits=char_traits<CharType>,    class Allocator=allocator<CharType> >class basic_string

typedef basic_string<char> string; typedef basic_string<wchar_t> wstring;

要使用string类型对象，必须包含相关头文件

#include <string>using std::string;string对象的定义和初始化：string s1;          //默认构造函数，s1为空串string s2(s1);      //将s2初始化为s1的一个副本string s3(“value”); //将s3初始化为一个字符串字面值副本string s4(n, ‘c’);  //将s4初始化为字符‘c’的n个副本

常用成员函数：
这里写图片描述

例程1：

#include <string>#include <iostream>using namespace std;int main(void){    string s1;    string s2("abcdefghijkl");    cout << s2 << endl;    basic_string<char> s3("xxx");   // 等价于string s3("xxx");    cout << s3 << endl;    string s4("abcdefg", 4);    cout << s4 << endl;    string s5(s2, 2, 3);    cout << s5 << endl;    string::iterator first = s2.begin() + 1;    string::iterator last = s2.begin() + 3;    string s6(first, last);     //[first, last)    cout << s6 << endl;    return 0;}

这里写图片描述
例程2：

#include <string>#include <iostream>using namespace std;int main(void){    string s1("abcdefdg");    cout << s1.size() << endl;    cout << s1.length() << endl;    cout << s1.empty() << endl;    cout << s1.substr(1, 2) << endl;    cout << s1.substr(1) << endl; //等价于s1.substr(1, -1);    string::size_type pos = s1.find('d', 1);//位置从0开始算起    if (pos == string::npos) //npos = -1        cout << "not found" << endl;    else        cout << "pos=" << pos << endl;    pos = s1.rfind('d');    if (pos == string::npos)        cout << "not found" << endl;    else        cout << "pos=" << pos << endl;    return 0;}

这里写图片描述
例程3：

#include <string>#include <iostream>using namespace std;int main(void){    string s1("abcdefghijkl");    s1.replace(2, 2, "AAAAAA");    cout << s1 << endl;    s1 = "abcdefg";    s1.replace(s1.begin() + 1, s1.begin() + 4, "AAAAAA");    cout << s1 << endl;    string s2 = "xyzabc";    s2.insert(2, "MMMM"); //在位置2之前插入    cout << s2 << endl;    s2.append("6666");    cout << s2 << endl;    string s3 = "111";    s2.swap(s3);    cout << s2 << endl;    cout << s3 << endl;    return 0;}

这里写图片描述
例程4：

#include <string>#include <iostream>using namespace std;void fun(char *str){    cout << str << endl;}int main(void){    string s1 = "abc";    s1[1] = 'B';    cout << s1 << endl;    const string s2 = "xyz";    //s2[1] = 'Y';      Error s2[1] 返回的是 const char&    string s3 = "111" + s1 + "222" ;    cout << s3 << endl;    //s3.c_str()    fun(const_cast<char *>(s3.c_str()));    return 0;}

这里写图片描述
例程5：

#include <string>#include <iostream>using namespace std;int main(){    string strinfo = " //*---Hello World!......------";    string strset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";    string::size_type first = strinfo.find_first_of(strset);    if(first == string::npos)        cout << "not find any characters" << endl;    string::size_type last = strinfo.find_last_of(strset);    if(last == string::npos)        cout << "not find any characters" << endl;    cout << strinfo.substr(first, last - first + 1) << endl;    return 0;}

输出：Hello World

可以利用find_first_of 等操作去除空格，如去除左空格可以这样：
string s = ” afas”;
string drop = ” \t”;
s.erase(0, s.find_first_not_of(drop));
去除右空格：
string s = ” dsfs “;
string drop = ” \t”;
s.erase(s.find_last_not_of(drop)+1);

参考：
C++ primer 第四版
Effective C++ 3rd
C++编程规范

转载http://blog.csdn.net/jnu_simba/article/details/9300811

0 0